CN110549745A

CN110549745A - Thermal printer

Info

Publication number: CN110549745A
Application number: CN201910993614.7A
Authority: CN
Inventors: 不公告发明人
Original assignee: 周洋洋
Current assignee: Suzhou Qingguo Intellectual Property Service Co.,Ltd.
Priority date: 2019-10-18
Filing date: 2019-10-18
Publication date: 2019-12-10
Anticipated expiration: 2039-10-18
Also published as: CN110549745B

Abstract

The invention relates to the field of thermal printing, in particular to a thermal printer which comprises a base, a shell assembly, a paper guide mechanism, a transmission mechanism, a heat dissipation mechanism and a thermal printing head, wherein the shell assembly is installed at the top of the base, a cavity is formed between the shell assembly and the base, a thermal insulation plate is installed in the cavity between the shell assembly and the base, a paper penetrating opening is formed in the thermal insulation plate, the paper guide mechanism is installed in the cavity on one side of the thermal insulation plate, the transmission mechanism is installed on the shell assembly on one side of the paper guide mechanism, the heat dissipation mechanism is installed on the shell assembly, and the thermal printing head is installed on the shell assembly on the top of. According to the invention, the influence of opening the cover and replacing the thermal sensitive paper tube on the thermal sensitive printing head is avoided through the arranged shell assembly, the paper guide mechanism is used for transmitting and limiting the paper, unqualified printing caused by the deviation of the paper is avoided, the limiting adjustment is convenient, the transmission mechanism is used for reducing the energy consumption, and the heat radiation mechanism is used for improving the heat radiation performance of the thermal sensitive printing head through heat transfer heat radiation and air circulation.

Description

thermal printer

Technical Field

The invention relates to the field of thermal printing, in particular to a thermal printer.

Background

The principle of a thermal printer is to coat a transparent film on a light-colored material (usually paper), heat the film for a period of time to change the color to a dark color (usually black or blue), and generate an image by heating a chemical reaction in the film, which is carried out at a certain temperature, and which is accelerated by the high temperature. When the temperature is lower than 60 ℃, the film needs to be changed into dark color for a long time, even for several years; when the temperature is 200 ℃, the reflection is completed within a few microseconds, the thermal printer selectively heats the thermal paper in a determined position, thereby generating a corresponding pattern, the heating is provided by a small electric heater on the print head in contact with the thermal material, the heater is logically controlled by the printer in the form of square dots or strips, and when activated, generates a pattern on the thermal paper corresponding to the heating element, the same logic circuit controlling the heating element, and the paper feed, thereby printing the pattern on the entire label or paper.

When the inside high temperature that appears of thermal printer, gather the loss at the inside temperature accelerating device of thermal printer casing, the flip that wholly sets up when uncapping and changing the thermal paper section of thick bamboo for it exposes to beat, and the difference of thermal printing paper width appears the drift easily at printing driven in-process, influences the regularity of printing and prints product quality.

Disclosure of Invention

To address the problems in the prior art, the present invention provides a thermal printer.

the technical scheme adopted by the invention for solving the technical problems is as follows: a thermal printer comprises a base, a shell component, a paper guide mechanism, a transmission mechanism, a heat dissipation mechanism and a thermal printing head, wherein the shell component is installed at the top of the base, a cavity is formed between the shell component and the base, a heat insulation plate is installed in the cavity between the shell component and the base, a paper penetrating port is formed in the heat insulation plate, the paper guide mechanism is installed in the cavity on one side of the heat insulation plate, the transmission mechanism is installed on the shell component on one side of the paper guide mechanism, the heat dissipation mechanism is installed on the shell component, the thermal printing head is installed on the shell component on the top of the paper guide mechanism, a bearing roller is installed on the shell component at the bottom of the thermal printing head, a thermal paper cylinder is rotatably installed in the cavity on one side, away from the thermal printing head, of the thermal printing head, a material guide roller is, the bottom of base fixed mounting has the removal wheel.

Specifically, the casing subassembly includes set casing, upset shell, pivot, inserted block and slot, the set casing is installed on the heat insulating board is close to the base of thermal printer head one side, the upset shell is rotated through the pivot and is installed on the base of keeping away from set casing one side, one side an organic whole that the pivot was kept away from to the upset shell is provided with the inserted block, the slot has been seted up to one side at heat insulating board top, equal fixed mounting has the magnetism that magnetism was inhaled mutually to inserted block and slot, the inserted block inserts inside the slot.

Specifically, lead paper mechanism including leading paper roll, spacing ring, stopper, thread bush, connecting rod and two-way threaded rod, it is provided with two, two to lead the paper roll and rotate and install in the both sides that the bearing roller is relative, two it is equipped with the spacing ring that two symmetries set up, two to lead the equal fixed mounting in top that the equal slip cap of paper roll was close to one side mutually has a stopper, two the bottom of spacing ring is all through connecting rod and thread bush fixed connection, two the equal symmetrical screw thread of thread bush on the spacing ring is installed on two-way threaded rod, the both ends that two-way threaded rod is relative are rotated and are installed on the casing subassembly of leading the paper roll bottom, just the screw thread symmetry on the two-way threaded rod sets up, casing subassembly and Z type turning handle fixed mounting are passed to the one end of.

Specifically, drive mechanism includes master gear, first from gear and second from the gear, master gear, first from gear and second from the gear all rotate to be installed on the inner wall of stationary housing one side, just the one end that the stationary housing was kept away from to the master gear is fixed mounting with the one end of bearing roller, the both sides that the master gear is relative are meshed respectively and are had first from gear and second from the gear, the one end of first following gear and second from the gear respectively with two paper guide roller fixed mounting, the one end that the bearing roller was kept away from to the master gear is connected with motor output through the shaft coupling, motor fixed mounting is on one side of casing subassembly.

Specifically, heat dissipation mechanism includes air intake, heat dissipation chamber, fin and cooling fan, install the air intake on the set casing, the heat dissipation chamber has been seted up on the base of set casing bottom, the inside fixed mounting in heat dissipation chamber has the fin, heat dissipation chamber bottom intercommunication has the thermovent, and the interior fixed mounting of thermovent has cooling fan.

Specifically, the top fixed mounting of air intake has the filter screen, the opening has been seted up on the set casing, the air intake is kept away from one side of filter screen and is inserted and install in the opening, just the width of filter screen is greater than the width of opening.

Specifically, the paper outlet has been seted up to the one side that the set casing keeps away from the heat insulating board, equal fixed mounting has the cut paper tooth on the diapire of paper outlet and the roof.

Specifically, the top wall of the bearing roller and the center of the paper penetrating opening, and the bottom wall of the guide roller and the center of the paper penetrating opening are arranged at the same horizontal height.

The invention has the beneficial effects that:

(1) The invention relates to a thermal printer, which is characterized in that a shell assembly arranged on a base is used, a cavity for thermal printing is formed between a fixed shell and a turnover shell and the base, a thermal insulation plate is used for separating the fixed shell and the turnover shell to form two cavities, so that a thermal printing and a thermal paper tube are replaced in the two cavities which are relatively independent, the influence of opening the cover to replace the thermal paper tube on a thermal printing head is avoided, meanwhile, the shell assembly realizes the dustproof protection of the thermal printing, a paper guide mechanism arranged at the bottom of the thermal printing head, two paper guide rollers symmetrically arranged on two sides of a supporting roller, two limiting rings and limiting blocks are arranged on the two paper guide rollers, the thermal paper passes through the two limiting rings and the limiting blocks to limit the paper transmission, the unqualified printing caused by the deviation of the paper is avoided, and the bottoms of the two limiting rings are connected with two thread sleeves on a, the rotation of two-way threaded rod can make two screw thread cover keep away from mutually or be close to the motion to spacing ring and the interval between the stopper on leading the paper roll are adjusted, make the spacing conduction that leads the paper roll and be fit for different width thermal sensitive paper, it is convenient to adjust, and lead the drive mechanism of installation between paper mechanism and the bearing roller, utilize the master gear and follow gear engagement with first from gear and second, realize two and lead same drives between paper roll and the bearing roller, reduce the energy consumption.

(2) According to the thermal printer, the air inlet is formed in the fixed shell, the heat dissipation cavity and the heat dissipation opening are formed in the base at the bottom of the thermal printing head, the heat dissipation fins are arranged inside the heat dissipation cavity, the heat dissipation fan is arranged inside the heat dissipation opening, heat inside the fixed shell is transferred to the heat dissipation cavity by utilizing the heat conduction performance of the heat dissipation fins, high-temperature air inside the fixed shell and the heat dissipation cavity is discharged from the heat dissipation opening under the action of the heat dissipation fan, external low-temperature air enters from the air inlet, heat dissipation is achieved through heat transfer, air circulation is promoted, the heat dissipation performance of the thermal printing head is effectively improved, the filter screen arranged on the air inlet prevents air from flowing into dust, and the practicability is higher.

Drawings

the invention is further illustrated with reference to the following figures and examples.

FIG. 1 is a schematic structural diagram of a thermal printer according to the present invention;

FIG. 2 is a side view of a thermal printer according to the present invention;

FIG. 3 is a schematic structural diagram of a paper guide mechanism of a thermal printer according to the present invention;

FIG. 4 is a schematic structural diagram of a transmission mechanism of a thermal printer according to the present invention;

FIG. 5 is an enlarged view of the point A shown in FIG. 2 according to the present invention;

Fig. 6 is a schematic structural diagram of an air inlet of a thermal printer according to the present invention.

In the figure: 1. a base; 2. a housing assembly; 21. a stationary case; 22. turning over the shell; 23. a rotating shaft; 24. inserting a block; 25. a slot; 3. a paper guide mechanism; 31. paper guide rollers; 32. a limiting ring; 33. a limiting block; 34. a threaded sleeve; 35. a connecting rod; 36. a bidirectional threaded rod; 4. a transmission mechanism; 41. a main gear; 42. a first slave gear; 43. a second slave gear; 5. a heat dissipation mechanism; 51. an air inlet; 52. filtering with a screen; 53. a heat dissipation cavity; 54. a heat sink; 55. a heat radiation fan; 6. a carrying roller; 7. a thermal print head; 8. a heat insulation plate; 81. a paper penetrating port; 9. a material guide roller; 10. a thermal sensitive paper cartridge; 11. a paper outlet; 12. cutting paper teeth; 13. the wheel is moved.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.

As shown in fig. 1-6, the thermal printer according to the present invention includes a base 1, a casing assembly 2, a paper guide mechanism 3, a transmission mechanism 4, a heat dissipation mechanism 5 and a thermal printing head 7, wherein the casing assembly 2 is installed on the top of the base 1, a cavity is formed between the casing assembly 2 and the base 1, a thermal insulation plate 8 is installed in the cavity between the casing assembly 2 and the base 1, a paper through opening 81 is formed in the thermal insulation plate 8, the paper guide mechanism 3 is installed in the cavity on one side of the thermal insulation plate 8, the transmission mechanism 4 is installed on the casing assembly 2 on one side of the paper guide mechanism 3, the heat dissipation mechanism 5 is installed on the casing assembly 2, the thermal printing head 7 is installed on the casing assembly 2 on the top of the paper guide mechanism 3, a bearing roller 6 is installed on the casing assembly 2 on the bottom of the thermal printing head 7, a thermal paper tube 10 is rotatably installed in the cavity on one side of the thermal insulation, a material guide roller 9 is arranged in a cavity between the thermal paper tube 10 and the thermal baffle 8, and a moving wheel 13 is fixedly arranged at the bottom of the base 1.

Specifically, casing subassembly 2 includes set casing 21, upset shell 22, pivot 23, inserted block 24 and slot 25, set casing 21 is installed on the base 1 that thermal baffle 8 is close to thermal print head 7 one side, upset shell 22 rotates through pivot 23 and installs on keeping away from base 1 of set casing 21 one side, one side an organic whole that pivot 23 was kept away from to upset shell 22 is provided with inserted block 24, slot 25 has been seted up to one side at thermal baffle 8 top, equal fixed mounting has the magnetism of inhaling mutually to detain on inserted block 24 and the slot 25, inserted block 24 inserts inside slot 25 for thermal print and thermal paper section of thick bamboo 10 are changed in two cavities independent relatively, avoid uncapping to change the influence of thermal paper section of thick bamboo 10 to thermal print head 7.

Specifically, the paper guide mechanism 3 comprises two paper guide rollers 31, two limiting rings 32, two limiting blocks 33, two threaded sleeves 34, two connecting rods 35 and a bidirectional threaded rod 36, the two paper guide rollers 31 are arranged on two opposite sides of the carrying roller 6 in a rotating mode, the two paper guide rollers 31 are sleeved with the two limiting rings 32 symmetrically arranged in a sliding mode, the two limiting rings 32 are fixedly arranged at the tops, close to one side, of the two limiting rings 32, the two limiting rings 32 are fixedly connected with the threaded sleeves 34 through the connecting rods 35, the two threaded sleeves 34 on the two limiting rings 32 are symmetrically arranged on the bidirectional threaded rod 36, the two opposite ends of the bidirectional threaded rod 36 are rotatably arranged on the shell assembly 2 at the bottom of the paper guide rollers 31, the threads on the bidirectional threaded rod 36 are symmetrically arranged, one end of the bidirectional threaded rod 36 penetrates through the shell assembly 2 and the Z-shaped rotating handle, the printing thermal paper passes through the two limiting rings 32 and the limiting blocks 33 to be limited in paper transmission, so that unqualified printing caused by paper deflection is avoided, the rotation of the bidirectional threaded rod 36 adjusts the spacing between the limiting rings 32 and the limiting blocks 33 on the paper guide roller 31, the paper guide roller 31 is suitable for limiting conduction of the thermal paper with different widths, and the adjustment is convenient.

Specifically, the transmission mechanism 4 includes a master gear 41, a first slave gear 42 and a second slave gear 43, the master gear 41, the first slave gear 42 and the second slave gear 43 are rotatably mounted on the inner wall of one side of the fixed housing 21, one end of the master gear 41 away from the fixed housing 21 is fixedly mounted on one end of the supporting roller 6, two opposite sides of the master gear 41 are respectively engaged with the first slave gear 42 and the second slave gear 43, one ends of the first slave gear 42 and the second slave gear 43 are respectively fixedly mounted on the two paper guide rollers 31, one end of the master gear 41 away from the supporting roller 6 is in transmission connection with an output end of a motor through a coupler, the motor is fixedly mounted on one side of the housing assembly 2, and by means of the engagement of the master gear 41 with the first slave gear 42 and the second slave gear 43, the motor drives the rotation of the master gear 41 and simultaneously drives the first slave gear 42 and the second slave gear 43 to rotate, the same driving between the two paper guide rollers 31 and the supporting roller 6 is realized, and the energy consumption is reduced.

specifically, the heat dissipation mechanism 5 includes an air inlet 51, a heat dissipation chamber 53, a heat dissipation fin 54 and a heat dissipation fan 55, the air inlet 51 is installed on the set casing 21, the heat dissipation chamber 53 has been seted up on the base 1 of the set casing 21 bottom, the inside fixed mounting in heat dissipation chamber 53 has the heat dissipation fin 54, the intercommunication in heat dissipation chamber 53 bottom has the thermovent, and the inside fixed mounting of thermovent has a heat dissipation fan 55, and under the effect of heat dissipation fan 55, the inside high temperature air in set casing 21 and heat dissipation chamber 53 is discharged by the thermovent, and outside low temperature air is got into by air inlet 51, dispels the heat through the heat transfer, and promotes the circulation of air, effectively improves the heat dissipation performance of.

Specifically, air intake 51's top fixed mounting has filter screen 52, the opening has been seted up on the set casing 21, air intake 51 keeps away from one side of filter screen 52 and inserts and install in the opening, just filter screen 52's width is greater than the width of opening, and air intake 51 inserts in the opening of set casing 21, conveniently dismantles it and carries out filter screen clearance, easy dismounting.

Specifically, exit slot 11 has been seted up to the one side that the heat insulating board 8 was kept away from to set casing 21, equal fixed mounting has cut paper tooth 12 on the diapire of exit slot 11 and the roof, and the convenience is torn the temperature sensitive paper that prints at exit slot 11.

Specifically, the top wall of the support roller 6 and the center of the paper passing hole 81, and the bottom wall of the guide roller 9 and the center of the paper passing hole 81 are all arranged at the same horizontal height, so that the thermal paper passing through the guide roller 9 and the support roller 6 horizontally passes through the paper passing hole 81.

When in use, firstly, the turnover shell 22 is rotated to open the upper cover of the printer, the thermal paper tube 10 is installed in the cavity of the printer, then the turnover shell 22 is rotated to enable the insertion block 24 to be inserted into the insertion slot 25, the thermal paper is stretched to enable the thermal paper to sequentially pass through the material guide roller 9, the paper passing port 81, the two paper guide rollers 31 and the bearing roller 6 and finally to be led out from the paper outlet 11, a semiconductor heating element is installed on a printing head, the printing head is heated and contacted with the thermal paper to print a required pattern, the image is generated by heating and generating chemical reaction in a film, a cavity for thermal printing is formed between the fixed shell 21 and the turnover shell 22 and the base 1 through the shell component 2 installed on the base 1, and the fixed shell 21 and the turnover shell 22 are separated by the thermal insulation plate 8 to form two cavities, so that the thermal printing and the thermal paper tube 10 are replaced in the two cavities which are relatively independent, the influence of a thermosensitive paper tube 10 on a thermosensitive printing head 7 is avoided to be replaced when the cover is opened, meanwhile, the shell component 2 realizes dustproof protection of thermosensitive printing, the paper guide mechanism 3 is arranged at the bottom of the thermosensitive printing head 7, the two paper guide rollers 31 are symmetrically arranged on two sides of the bearing roller 6, the two paper guide rollers 31 are respectively provided with two limiting rings 32 and limiting blocks 33, the thermosensitive paper to be printed passes through the two limiting rings 32 and the limiting blocks 33 to carry out paper transmission limiting, unqualified printing caused by paper deflection is avoided, the bottoms of the two limiting rings 32 are connected with the two thread sleeves 34 on the bidirectional threaded rod 36 through the connecting rod 35, the two thread sleeves 34 can move far away or close to each other through the rotation of the bidirectional threaded rod 36, so that the distance between the limiting rings 32 and the limiting blocks 33 on the paper guide rollers 31 is adjusted, and the paper guide rollers 31 are suitable, the adjustment is convenient, the transmission mechanism 4 arranged between the paper guide mechanism 3 and the bearing roller 6 utilizes the master gear 41 to be meshed with the first slave gear 42 and the second slave gear 43, the motor drives the master gear 41 to rotate and simultaneously drives the first slave gear 42 and the second slave gear 43 to rotate, the same drive between the two paper guide rollers 31 and the bearing roller 6 is realized, the energy consumption is reduced, through the arranged heat dissipation mechanism 5, the air inlet 51 arranged on the fixed shell 21, the heat dissipation cavity 53 arranged on the base 1 at the bottom of the thermal printing head 7 and a heat dissipation port are arranged, the heat dissipation fin 54 is arranged in the heat dissipation cavity 53, the heat dissipation fan 55 is arranged in the heat dissipation port, the heat in the fixed shell 21 is transmitted to the heat dissipation cavity 53 by utilizing the heat conduction performance of the heat dissipation fin 54, the high-temperature air in the fixed shell 21 and the heat dissipation cavity 53 is discharged from the heat dissipation port under the action of the heat dissipation fan 55, the external low-, through heat transfer heat dissipation and promotion circulation of air, effectively improve the heat dispersion of thermal printhead 7, and the filter screen 52 of installation on air intake 51 prevents that the air circulation from advancing the dirt, and the practicality is stronger.

The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and the embodiments and descriptions given above are only illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A thermal printer, characterized by: comprises a base (1), a shell component (2), a paper guide mechanism (3), a transmission mechanism (4), a heat dissipation mechanism (5) and a thermal printing head (7), wherein the shell component (2) is installed at the top of the base (1), a cavity is formed between the shell component (2) and the base (1), a heat insulation plate (8) is installed in the cavity between the shell component (2) and the base (1), a paper penetrating port (81) is formed in the heat insulation plate (8), the paper guide mechanism (3) is installed in the cavity on one side of the heat insulation plate (8), the transmission mechanism (4) is installed on the shell component (2) on one side of the paper guide mechanism (3), the heat dissipation mechanism (5) is installed on the shell component (2) at the top of the paper guide mechanism (3), the thermal printing head (7) is installed on the shell component (2) at the bottom of the thermal printing head (7), a bearing roller (6) is installed on the shell component (2) at the, the thermal printing head is characterized in that a thermal paper tube (10) is rotatably mounted in a cavity on one side, away from the thermal printing head (7), of the thermal insulation plate (8), a guide roller (9) is mounted in the cavity between the thermal paper tube (10) and the thermal insulation plate (8), and a moving wheel (13) is fixedly mounted at the bottom of the base (1).

2. A thermal printer according to claim 1, wherein: casing subassembly (2) are including set casing (21), upset shell (22), pivot (23), inserted block (24) and slot (25), install on base (1) that thermal baffle (8) are close to thermal print head (7) one side fixed casing (21), upset shell (22) are rotated through pivot (23) and are installed on base (1) of keeping away from set casing (21) one side, one side an organic whole that pivot (23) were kept away from in upset shell (22) is provided with inserted block (24), slot (25) have been seted up to one side at thermal baffle (8) top, equal fixed mounting has the magnetism of magnetism looks absorption to detain on inserted block (24) and slot (25), inserted block (24) insert inside slot (25).

3. A thermal printer according to claim 1, wherein: the paper guide mechanism (3) comprises paper guide rollers (31), two limiting rings (32), two limiting blocks (33), thread sleeves (34), connecting rods (35) and a bidirectional threaded rod (36), the paper guide rollers (31) are provided with two, the two paper guide rollers (31) are rotatably installed on two opposite sides of a bearing roller (6), the two paper guide rollers (31) are respectively sleeved with the two limiting rings (32) which are symmetrically arranged in a sliding manner, the two limiting rings (32) are respectively fixedly installed at the top parts, close to one side, of the two limiting rings (32), the bottoms of the two limiting rings (32) are respectively fixedly connected with the thread sleeves (34) through the connecting rods (35), the thread sleeves (34) on the two limiting rings (32) are respectively installed on the bidirectional threaded rod (36) in a symmetrical manner, the two opposite ends of the bidirectional threaded rod (36) are rotatably installed on a shell assembly (2) at the bottom of the paper guide rollers (31), and the threads on the bidirectional threaded rod (36) are symmetrically arranged, and one end of the bidirectional threaded rod (36) penetrates through the shell component (2) and is fixedly installed with the Z-shaped rotating handle.

4. A thermal printer according to claim 1, wherein: the transmission mechanism (4) comprises a main gear (41), a first slave gear (42) and a second slave gear (43), wherein the main gear (41), the first slave gear (42) and the second slave gear (43) are rotatably mounted on the inner wall of one side of the fixed shell (21), one end, far away from the fixed shell (21), of the main gear (41) is fixedly mounted with one end of the bearing roller (6), two opposite sides of the main gear (41) are respectively meshed with the first slave gear (42) and the second slave gear (43), one ends of the first slave gear (42) and the second slave gear (43) are respectively fixedly mounted with the two paper guide rollers (31), one end, far away from the bearing roller (6), of the main gear (41) is in transmission connection with the output end of the motor through a coupler, and the motor is fixedly mounted on one side of the shell assembly (2).

5. a thermal printer according to claim 2, wherein: heat dissipation mechanism (5) include air intake (51), heat dissipation chamber (53), fin (54) and radiator fan (55), install air intake (51) on set casing (21), heat dissipation chamber (53) have been seted up on base (1) of set casing (21) bottom, the inside fixed mounting in heat dissipation chamber (53) has fin (54), heat dissipation chamber (53) bottom intercommunication has the thermovent, and the fixed mounting has radiator fan (55) in the thermovent.

6. The thermal printer according to claim 5, wherein: the top fixed mounting of air intake (51) has filter screen (52), the opening has been seted up on set casing (21), one side that filter screen (52) were kept away from in air intake (51) is inserted and is installed in the opening, just the width of filter screen (52) is greater than the width of opening.

7. A thermal printer according to claim 2, wherein: paper outlet (11) have been seted up to one side that fixed shell (21) kept away from heat insulating board (8), equal fixed mounting has cut paper tooth (12) on the diapire of paper outlet (11) and the roof.

8. A thermal printer according to claim 1, wherein: the top wall of the bearing roller (6) and the center of the paper passing opening (81) as well as the bottom wall of the guide roller (9) and the center of the paper passing opening (81) are arranged at the same horizontal height.