CN220129787U - A clean structure of printhead for inkjet printing equipment - Google Patents

Abstract

The present utility model relates to a print head cleaning structure for an inkjet printing apparatus, comprising: the first sliding seat can move back and forth relative to the printing head; the scraping blade is arranged on the first sliding seat, and in the working state of the scraping blade, the scraping end of the scraping blade is contacted with the surface of the spray hole at the bottom of the printing head in the process that the first sliding seat moves back and forth relative to the printing head; in a non-working state, the scraping end on the scraping blade is separated from the surface of the spray hole at the bottom of the printing head; the method is characterized in that: the collecting box is hollow in the collecting box, and a collecting cavity with an opening is formed at the top of the collecting box; when the wiper blade is in a non-working state, the surface energy of the spray hole at the bottom of the printing head is in sealing connection with the periphery of the opening of the collecting cavity; the waste ink bin is communicated with the collecting cavity through a first pipeline; and the negative pressure generating device is used for generating negative pressure in the first pipeline. The cleaning structure can clean and recycle dry ink in the spray hole, and improves the printing effect of the ink-jet printer.

Description

A clean structure of printhead for inkjet printing equipment

Technical Field

The utility model relates to the technical field of ink-jet printing, in particular to a printing head cleaning structure for ink-jet printing equipment.

Background

Ink droplets required for an inkjet printer are typically stored in an ink cartridge of the inkjet printer, the ink cartridge having an inkjet head (print head) at its bottom end. In the process of printing paper, the ink jet head can jet ink drops in the ink cartridge to the paper through the nozzle surface on the surface of the ink jet head to form characters or patterns so as to perform printing work.

After the ink droplets are ejected from the ink jet head of the ink jet printer, residual ink is relatively generated and attached to the nozzle surface. After the residual ink reaches a certain amount, the ink can be prevented from being ejected if the processing is not fast enough, the nozzle surface can be blocked after the ink is dried, or the residual ink can drop onto paper during printing, so that the paper is polluted. Then, after the ink jet head performs a number of back and forth printing operations, the ink jet head needs to be controlled to temporarily stop the printing operation and move to a cleaning area of the ink jet printer to perform the cleaning operation so as to scrape residual ink on the nozzle surface.

In order to solve the technical problem, chinese utility model with patent No. ZL202020897323.6 (grant publication No. CN 212827412U) discloses a print head cleaning device, which comprises a base component and a wiper blade arranged on the base component, wherein the wiper blade is an elastic sheet body capable of bending to one side when contacting with a print head, the top of the elastic sheet body is provided with a scraping end, the base component is provided with an inserting port part for inserting the root of the elastic sheet body, the inserting port part comprises a first blocking wall and a second blocking wall which respectively prop against the front side and the rear side of the elastic sheet body, and the heights of the first blocking wall and the second blocking wall are different, so that the elastic sheet body has different bending degrees when bending to the front side and the rear side respectively. In the process that the printing head is close to the scraping blade and contacts with the scraping blade, the scraping blade can bend towards one side of the blocking wall with relatively low height, at the moment, the scraping blade can bend to a large extent, the acting force which is propped against the bottom of the printing head is relatively small, and the resistance between the scraping blade and the glue bulges at the bottom of the printing head is effectively reduced, so that the scraping blade can slide smoothly relative to the printing head.

Although the cleaning device for the printing head can realize residual ink on the surface of the nozzle, after the ink jet printer in the prior art is not used for a long time, the ink in the spray hole is also dried, and the cleaning device can not process the dried ink in the spray hole, so that after-sale cleaning is needed in the actual use process, and the user experience is affected. For this reason, further improvements to the prior art are needed.

Disclosure of Invention

The utility model aims to solve the technical problem of providing a printing head cleaning structure for an ink jet printing device, which can automatically clean dry ink in a spray hole.

The technical scheme adopted for solving the technical problems is as follows: a printhead cleaning structure for an inkjet printing apparatus, comprising:

the first sliding seat can move back and forth relative to the printing head;

the scraping blade is arranged on the first sliding seat and provided with a scraping end capable of scraping waste ink at the spray hole at the bottom of the printing head, the scraping blade is provided with an operating state and a non-operating state in the process that the first sliding seat moves back and forth relative to the printing head, and the scraping end on the scraping blade is contacted with the surface of the spray hole at the bottom of the printing head in the operating state; in a non-working state, the scraping end on the scraping blade is separated from the surface of the spray hole at the bottom of the printing head;

the method is characterized in that: and also comprises

The collecting box is arranged below the printing head, and the collecting box is hollow inside to form a collecting cavity with an opening at the top; when the wiper blade is in a non-working state, the surface energy of the spray hole at the bottom of the printing head is in sealing connection with the periphery of the opening of the collecting cavity;

the waste ink bin is communicated with the collecting cavity through a first pipeline;

and the negative pressure generating device is used for generating negative pressure in the first pipeline.

In order to improve the sealing effect, a sealing element for forming sealing fit with the bottom of the printing head is arranged on the periphery of the opening of the collecting cavity.

In order to perform coarse-step filtration on the waste ink, a filter screen plate is restrained in the collecting cavity, and a filter mesh for filtering the coarse waste ink is arranged on the filter screen plate.

In order to facilitate the installation of the first pipeline, so as to realize the communication between the collecting cavity and the first pipeline, the bottom of the collecting cavity is provided with a through hole and a second pipeline extending downwards from the through hole, and the second pipeline is communicated with the first pipeline.

In order to drive the first sliding seat to move back and forth, a driving mechanism for driving the first sliding seat to move back and forth is further included, the driving mechanism includes:

a base;

the second sliding seat is restrained on the base in a mode of being capable of moving left and right relative to the base;

the transmission mechanism is arranged on the second sliding seat and is in transmission connection with the base and the first sliding seat, and the transmission mechanism can drive the first sliding seat to move back and forth along with the left and right movement of the second sliding seat. After the carriage of the ink-jet printing device completes the printing task, the carriage moves rightward, so that the second sliding seat can move rightward and leftward under the action of the carriage of the ink-jet printing device.

In order to realize buffering when collecting the box and printing the head contact and improve the reliability of printing the head contact, preferably, be equipped with the concave part of undercut and the bayonet socket that the adjacent concave part set up on the second sliding seat, the through-hole that supplies the first pipeline to wear to establish is seted up to the centre of concave part, the second pipeline is equipped with the elastic component with the first pipeline overcoat that stretches into in the concave part from the through-hole, be equipped with the supporting legs who wears to locate in the bayonet socket on the collecting box, the bottom of supporting legs is equipped with the card foot, the elastic component acts on the collecting box, so that the collecting box keeps the trend of orientation printing the head bottom motion and messenger's collecting box through card foot joint on the second sliding seat all the time.

In order to collect waste ink after the scraping operation of the scraping blade is finished, preferably, the first sliding seat is provided with an installation space which is arranged along the front-back direction and is used for installing the collecting box, the rear side of the installation space is provided with an opening, the scraping blade is arranged at the rear side of the installation space and is adjacent to the installation space, and the collecting box can be moved out from the opening at the rear side of the installation space in the process that the second sliding seat moves from left to right relative to the base to drive the first sliding seat to move forwards from back to back. After the collecting box is moved out of the rear side opening of the installation space, the scraping blade is positioned at the front side of the collecting box, so that the collecting box can work, and interference of the scraping blade is avoided.

In order to realize that the second sliding seat can move left and right relative to the base, the front side and the rear side on the base are provided with first sliding grooves which transversely extend, the front side and the rear side of the second sliding seat are provided with first sliding columns which extend outwards, and the first sliding columns can correspondingly penetrate through the first sliding grooves.

In order to make the waste ink collecting effect of the collecting box better after the waste ink scraping operation is finished, preferably, the first sliding groove comprises a continuous translation section and a smooth ascending section, the smooth ascending section is positioned on the right side of the translation section, and the scraping blade is in an operating state in a state that the first sliding column of the second sliding seat is positioned in the translation section of the first sliding groove; and in the state that the first sliding column of the second sliding seat is positioned at the tail end of the smooth ascending section of the first sliding groove, the surface of the spray hole at the bottom of the printing head can be in sealing connection with the peripheral edge of the opening of the collecting cavity. In this way, when the wiper blade is in a non-working state, the second sliding seat is integrally lifted up through the smooth lifting section, so that the collection box mounted on the second sliding seat can be conveniently contacted with the surface of the spray hole at the bottom of the printing head.

The structure of the transmission mechanism is various, preferably, the transmission mechanism comprises a transmission shaft penetrating through the second sliding seat, a first gear arranged at the upper end of the transmission shaft and a second gear arranged at the lower end of the transmission shaft, the first sliding seat is provided with a first rack extending along the front-back direction and meshed with the first gear, and the base is provided with a second rack extending along the left-right direction and meshed with the second gear.

Compared with the prior art, the utility model has the advantages that: through setting up collection box, useless ink storehouse and the negative pressure generating device that have the collection chamber to under the doctor-bar was in non-operating condition, form sealing connection between the orifice place surface energy of printhead bottom and the uncovered week edge of collection chamber, so utilize the negative pressure effect in the first pipeline can take away the inside dry ink of printhead bottom orifice, make the new ink outflow in the printhead bottom orifice, useless ink will carry to useless ink storehouse through first pipeline and retrieve. Thereby realizing the cleaning and recovery of the dry ink in the spray hole and improving the printing effect of the ink-jet printer.

Drawings

FIG. 1 is a schematic view of a printhead cleaning structure (a second sliding seat is at an initial position) according to an embodiment of the present utility model;

FIG. 2 is a schematic view of a portion of the structure from another perspective of FIG. 1;

FIG. 3 is a top view of FIG. 1;

FIG. 4 is an exploded view of FIG. 1;

FIG. 5 is a schematic view of the printhead cleaning structure of FIG. 1 (omitting the collection cartridge, waste ink reservoir and negative pressure generating device);

FIG. 6 is a schematic view of a printhead cleaning structure according to an embodiment of the present utility model (the second sliding seat is at the end position);

FIG. 7 is a schematic view of another view angle structure of FIG. 6;

FIG. 8 is a schematic view of the printhead cleaning structure of FIG. 6 (omitting the collection cartridge, waste ink reservoir and negative pressure generating device);

fig. 9 is a partial cross-sectional view of fig. 6.

Detailed Description

The utility model is described in further detail below with reference to the embodiments of the drawings.

As shown in fig. 1 to 9, the print head cleaning structure for an inkjet printing apparatus in this embodiment includes a first slide holder 1, a blade 3, a collection box 42, a waste ink tank 5, and a negative pressure generating device 6.

Wherein the first sliding seat 1 can move back and forth relative to the printing head 2; the scraping blade 3 is arranged on the first sliding seat 1 and provided with a scraping end 31 capable of scraping waste ink at the spray hole 21 at the bottom of the printing head 2, the scraping blade 3 has an operating state and a non-operating state in the process that the first sliding seat 1 moves back and forth relative to the printing head 2, and the scraping end 31 on the scraping blade 3 is contacted with the surface of the spray hole 21 at the bottom of the printing head 2 in the operating state; in the non-working state, the scraping end 31 on the scraping blade 3 is separated from the surface of the spray hole 21 at the bottom of the printing head 2 and is positioned at the front end of the printing head 2; at least the scraping end 31 of the scraping blade 3 is made of a deformable material, so that each scraping blade 3 can swing back and forth when contacting with the bottom of the printing head 2, and the scraping end 31 of the scraping blade 3 is closely contacted with the position of the spray hole 21, thereby realizing the cleaning of ink or dirt.

The collecting box 42 is arranged below the printing head 2, and the collecting box 42 is hollow to form a collecting cavity 421 with an open top; and when the wiper blade 3 is in a non-working state, the surface of the spray hole 21 at the bottom of the printing head 2 can be in sealing connection with the periphery of the opening of the collecting cavity 421, and the periphery of the opening of the collecting cavity 421 is provided with a sealing piece 422 which is used for forming sealing fit with the bottom of the printing head 2, and the sealing piece 422 is made of rubber materials so as to improve the sealing effect; the waste ink bin 5 is communicated with the collecting cavity 421 through a first pipeline a, and the first pipeline a is a telescopic pipe; the negative pressure generating device 6 is used for generating negative pressure in the first pipeline a. In this embodiment, the negative pressure generating device 6 is configured to generate negative pressure by extruding the first pipeline a through a gear transmission manner of a carriage assembly of the inkjet printing apparatus, so that the negative pressure is generated by using the movement force of the carriage assembly, without additional driving force, other negative pressure generating devices in the prior art can be adopted, and no further description is provided herein.

In this embodiment, the bottom of the collecting cavity 421 is provided with a through hole 420 and a second pipe b extending downward from the through hole 420, and the second pipe b is communicated with the first pipe a; and the filter screen plate 423 is restrained in the collecting chamber 421, the filter screen plate 423 is provided with a filter mesh (in this embodiment, the filter mesh is not shown in fig. 1 to 9, but should be actually provided, and the filter screen mesh is sized to filter the coarse waste ink to prevent the second pipe b and the first pipe a from being blocked), so that the wiper blade 3 is driven by the first sliding seat 1 to move back and forth, thereby realizing the waste ink scraping operation at the position of the nozzle 21, and the collecting box 42 sucks the waste ink on the nozzle 21 and the ink remained in the nozzle 21 under the action of negative pressure, so as to improve the cleaning effect of the residual ink.

The device also comprises a driving mechanism for driving the first sliding seat 1 to move back and forth, wherein the driving mechanism comprises a base 71, a second sliding seat 72 and a transmission mechanism, and the second sliding seat 72 is restrained on the base 71 in a mode of being capable of moving left and right relative to the base 71; the transmission mechanism is arranged on the second sliding seat 72 and is in transmission connection with the base 71 and the first sliding seat 1, and the transmission mechanism can move left and right along with the second sliding seat 72 to drive the first sliding seat 1 to move back and forth. As shown in fig. 4, the transmission mechanism in this embodiment includes a transmission shaft 731 penetrating through the second sliding seat 72, a first gear 732 disposed at an upper end of the transmission shaft 731, and a second gear 733 disposed at a lower end of the transmission shaft 731, a first rack 11 extending in a front-rear direction and engaged with the first gear 732 is disposed on the first sliding seat 1, and a second rack 711 extending in a left-right direction and engaged with the second gear 733 is disposed on the base 71.

The second sliding seat 72 is provided with a concave portion 721 recessed downwards and a bayonet 722 arranged adjacent to the concave portion 721, a through hole 7211 for the first pipeline a to pass through is formed in the center of the concave portion 721, an elastic member 8 is sleeved outside the second pipeline b and the first pipeline a extending into the concave portion 721 from the through hole 7211, a supporting leg 424 passing through the bayonet 722 is arranged on the collecting box 42, a clamping leg 425 is arranged at the bottom of the supporting leg 424, the elastic member 8 acts on the collecting box 42 (as shown in fig. 9, the elastic member 8 is a spring, a first end of the spring is supported at the bottom of the concave portion 721, and a second end of the spring is supported at the lower surface of the collecting box 42), so that the collecting box 42 always keeps moving towards the bottom of the printing head 2, and the collecting box 42 is clamped on the second sliding seat 72 through the clamping leg 425. In this embodiment, the first pipe a is a telescopic pipe, so that the communication with the second pipe b can be continuously maintained even when the second sliding seat 72 moves, as shown in fig. 9, two supporting legs 424 are provided, and one clamping leg 425 is correspondingly provided on each supporting leg 424.

The front and rear sides of the base 71 are respectively provided with a first sliding groove 712 extending transversely, the front and rear sides of the second sliding seat 72 are respectively provided with a first sliding column 723 extending outwards, and the first sliding columns 723 can correspondingly penetrate the first sliding grooves 712. Similarly, the first sliding seat 1 has second sliding columns 13 extending outwards on the left and right sides, the second sliding seat 72 has second sliding grooves 725 extending longitudinally on the left and right sides, the second sliding columns 13 can be correspondingly inserted into the second sliding grooves 725, the second sliding seat 72 also has a pillar 724, when the print head 2 can touch the pillar 724 after printing is completed, so as to drive the second sliding seat 72 to move laterally, specifically, the print head 2 can drive the second sliding seat 72 to slide laterally from the initial position to the final position. The initial position of the second sliding seat 72 is shown in fig. 1, and the final position of the second sliding seat 72 is shown in fig. 6.

The first sliding seat 1 is provided with a mounting space 12 arranged along the front-rear direction for mounting the collecting box 42, the rear side of the mounting space 12 is provided with an opening, the scraping blade 3 is arranged at the rear side of the mounting space 12 and is adjacent to the mounting space 12, and the collecting box 42 can be moved out of the opening at the rear side of the mounting space 12 in the process that the second sliding seat 72 moves from left to right relative to the base 71 to drive the first sliding seat 1 to move forwards from rear to rear.

The first sliding groove 712 includes a continuous translation section 7121 (the length of which is approximately the same as the length of the bottom of the print head 2) and a smooth rising section 7122, the smooth rising section 7122 being located on the right side of the translation section 7121, and the wiper blade 3 is in an operating state in a state in which the first sliding column 723 of the second sliding seat 72 is located in the translation section 7121 of the first sliding groove 712; in a state where the first slide column 723 of the second slide base 72 is in the smoothly rising section 7122 of the first slide groove 712, the wiper blade 3 is in a non-operating state. Due to the presence of the smoothly rising section 7122, the second sliding seat 72 rises after moving laterally a certain distance, so that the collection box 42 restrained on the second sliding seat 72 is closer to the bottom of the print head 2, and in a state that the first sliding column 723 of the second sliding seat 72 is located at the end of the smoothly rising section 7122 of the first sliding groove 712, the surface of the nozzle hole 21 at the bottom of the print head 2 can form a sealing connection with the open peripheral edge of the collection chamber 421.

The working procedure in this embodiment is: after the printing head 2 finishes the printing work, the printing head 2 can contact with the second sliding seat 72 and continuously drive the second sliding seat 72 to transversely slide from the initial position to the final position relative to the base 71, as shown in fig. 1, which is a schematic view of the state in which the second sliding seat 72 is located at the initial position, and fig. 6, which is a schematic view of the state in which the second sliding seat 72 is located at the final position; in this process, the second slide base 72 and the printhead 2 remain relatively stationary, and during the lateral movement of the second slide base 72, the first gear 732 and the second gear 733 coaxially disposed on the transmission mechanism cooperate with the first rack 11 on the first slide base 1 and the second rack 711 on the base 71, respectively, so as to convert the lateral movement of the second slide base 72 relative to the base 71 into the longitudinal movement of the first slide base 1 relative to the second slide base 72. For specific structure, reference is also made to the disclosure of the chinese patent application No. ZL202020897323.6 (issued to CN 212827412U) by the inventor of the present utility model.

In this process, the wiper 3 fixed on the first sliding seat 1 can also longitudinally slide relative to the printhead 2 (the nozzle 21 at the bottom of the printhead 2 is arranged in a longitudinal arrangement), and in the process of the longitudinal sliding of the wiper 3, the scraping end 31 on the wiper 3 contacts with the surface of the nozzle 21 at the bottom of the printhead 2; when the first sliding column 723 of the second sliding seat 72 slides laterally to the end position of the translation section 7121 of the first sliding groove 712, the wiper 3 can drop from the bottom of the print head 2, the wiper 3 temporarily stays at the front end position of the print head 2, and when the first sliding column 723 of the second sliding seat 72 is at the end of the smooth rising section 7122 of the first sliding groove 712 (i.e. corresponds to the end position), the second sliding seat 72 rises integrally and drives the collecting box 42 to rise integrally, so that the surface of the nozzle 21 at the bottom of the print head 2 can form a sealing connection with the sealing member 422 at the periphery of the opening of the collecting cavity 421, as shown in fig. 8, the dried ink in the nozzle 21 at the bottom of the print head 2 can be taken away by the negative pressure action in the first pipeline a, so that new ink flows out into the collecting cavity 421, and the waste ink flows into the second pipeline b through the through holes 420 on the collecting box 42 and is conveyed to the waste ink bin 5 through the first pipeline a.

Claims (10)

1. A printhead cleaning structure for an inkjet printing apparatus, comprising:

a first slide seat (1) capable of moving back and forth relative to the print head (2);

the scraping blade (3) is arranged on the first sliding seat (1) and provided with a scraping end (31) capable of scraping waste ink at the spray hole (21) at the bottom of the printing head (2), the scraping blade (3) has an operating state and a non-operating state in the process that the first sliding seat (1) moves back and forth relative to the printing head (2), and the scraping end (31) on the scraping blade (3) is in contact with the surface of the spray hole (21) at the bottom of the printing head (2) in the operating state; in a non-working state, the scraping end (31) on the scraping blade (3) is separated from the surface of the spray hole (21) at the bottom of the printing head (2);

the method is characterized in that: and also comprises

The collecting box (42) is arranged below the printing head (2), and a collecting cavity (421) with an opening at the top is formed in the collecting box (42); when the wiper blade (3) is in a non-working state, the surface of the spray hole (21) at the bottom of the printing head (2) can be in sealing connection with the periphery of the opening of the collecting cavity (421);

the waste ink bin (5) is communicated with the collecting cavity (421) through a first pipeline (a);

and a negative pressure generating device (6) for generating a negative pressure in the first pipe (a).

2. The printhead cleaning structure of claim 1, wherein: a seal (422) for forming a sealing fit with the bottom of the printing head (2) is arranged at the periphery of the opening of the collecting cavity (421).

3. The printhead cleaning structure of claim 2, wherein: the filter screen plate (423) is restrained in the collecting cavity (421), and the filter screen plate (423) is provided with filter meshes for filtering coarse waste ink.

4. A printhead cleaning structure according to claim 3, wherein: the bottom of the collecting cavity (421) is provided with a through hole (420) and a second pipeline (b) extending downwards from the through hole (420), and the second pipeline (b) is communicated with the first pipeline (a).

5. The printhead cleaning structure of claim 4, wherein: the device also comprises a driving mechanism for driving the first sliding seat (1) to move back and forth, and the driving mechanism comprises:

a base (71);

a second slide seat (72) which is constrained to the base (71) so as to be movable laterally with respect to the base (71);

the transmission mechanism is arranged on the second sliding seat (72) and is in transmission connection with the base (71) and the first sliding seat (1), and the transmission mechanism can drive the first sliding seat (1) to move back and forth along with the left-right movement of the second sliding seat (72).

6. The printhead cleaning structure of claim 5, wherein: the printing device is characterized in that a concave part (721) recessed downwards and a bayonet (722) adjacent to the concave part (721) are arranged on the second sliding seat (72), a through hole (7211) for the first pipeline (a) to penetrate is formed in the center of the concave part (721), an elastic piece (8) is sleeved outside the second pipeline (b) and the first pipeline (a) extending into the concave part (721) from the through hole (7211), supporting feet (424) penetrating into the bayonet (722) are arranged on the collecting box (42), clamping feet (425) are arranged at the bottoms of the supporting feet (424), and the elastic piece (8) acts on the collecting box (42) so that the collecting box (42) always keeps a trend of moving towards the bottom of the printing head (2) to enable the collecting box (42) to be clamped on the second sliding seat (72) through the clamping feet (425).

7. The printhead cleaning structure of claim 6, wherein: the cleaning device is characterized in that the first sliding seat (1) is provided with an installation space (12) which is arranged along the front-back direction and is used for installing the collecting box (42), the rear side of the installation space (12) is provided with an opening, the scraping blade (3) is arranged on the rear side of the installation space (12) and is adjacent to the installation space (12), and the second sliding seat (72) moves from left to right relative to the base (71) to drive the first sliding seat (1) to move forwards from back to back, and the collecting box (42) can move out from the opening on the rear side of the installation space (12).

8. The printhead cleaning structure according to any one of claims 5 to 7, wherein: the base (71) is provided with a first sliding groove (712) extending transversely on the front side and the rear side, the second sliding seat (72) is provided with a first sliding column (723) extending outwards on the front side and the rear side, and the first sliding column (723) can be correspondingly arranged in the first sliding groove (712) in a penetrating mode.

9. The printhead cleaning structure of claim 8, wherein: the first sliding groove (712) comprises a continuous translation section (7121) and a smooth ascending section (7122), the smooth ascending section (7122) is positioned on the right side of the translation section (7121), and the wiper blade (3) is in a working state in the state that the first sliding column (723) of the second sliding seat (72) is positioned in the translation section (7121) of the first sliding groove (712); in the state that the first sliding column (723) of the second sliding seat (72) is positioned at the smooth ascending section (7122) of the first sliding groove (712), the wiper blade (3) is positioned at the non-working state, and in the state that the first sliding column (723) of the second sliding seat (72) is positioned at the tail end of the smooth ascending section (7122) of the first sliding groove (712), the surface of the spray hole (21) at the bottom of the printing head (2) can be in sealing connection with the periphery of the opening of the collecting cavity (421).

10. The printhead cleaning structure according to any one of claims 5 to 7, wherein: the transmission mechanism comprises a transmission shaft (731) penetrating through the second sliding seat (72), a first gear (732) arranged at the upper end of the transmission shaft (731) and a second gear (733) arranged at the lower end of the transmission shaft (731), a first rack (11) extending along the front-back direction and meshed with the first gear (732) is arranged on the first sliding seat (1), and a second rack (711) extending along the left-right direction and meshed with the second gear (733) is arranged on the base (71).