Microscope dark field illumination system capable of being additionally installed

Abstract

The invention relates to the technical field of microscopes, in particular to a microscope dark field illumination system capable of being additionally mounted, which comprises a mounting seat movably mounted on an objective lens seat, an annular dark field cavity is coaxially formed in the mounting seat, an opening ring groove is formed in the end part of the dark field cavity, a collimating light lens seat is arranged in the dark field cavity, and a collimating light source is arranged in the collimating light lens seat. A light focusing base is arranged at the joint of the dark field cavity and the open ring groove, and LED lamp beads are arranged in the dark field cavity. According to the microscope dark field illumination system capable of being additionally installed, the LED lamp beads arranged in the installation base can emit light, and the emitted light is emitted out of the open annular groove of the dark field cavity through the collimating light lens base and the light focusing base so as to be located on the lower side of the installation base to form a coaxial annular aperture; the mounting seat can be directly and coaxially mounted on the objective lens seat so as to form a coaxial annular aperture below the objective lens seat for light supplement, and the opening and closing of the light supplement aperture can be directly realized by controlling the opening and closing of the LED lamp beads.

Description

Technical Field

[0001] The invention relates to the technical field of microscopes, and in particular to a microscope dark field illumination system that can be additionally installed. Background Art

[0002] When using a microscope, a light source is often needed to provide supplementary light to the lower side of the objective lens.

[0003] When supplementing light from the bottom side of an object, the objective lens is usually replaced with an epi-lens. An epi-lens fluorescence microscope illuminates the specimen through a light source, excites the fluorescent substance to emit fluorescence, and then transmits the fluorescence signal to the detector through the objective lens and condenser. This design eliminates the need for transmitted light for the specimen, making it possible to observe opaque or translucent specimens, such as thick slices, filter membranes, colonies, and tissue culture specimens.

[0004] Including the above-mentioned prior art, in actual use, it is necessary to frequently replace ordinary objective lenses or epi-lenses to meet the fill-light requirements of different specimens, which makes the use of the microscope inconvenient. Secondly, the reciprocating disassembly and assembly of the microscope lens can easily cause damage to the microscope body. Summary of the invention

[0005] The purpose of the present invention is to provide a microscope dark field illumination system that can be additionally installed to solve the above-mentioned problem.

[0006] In order to achieve the above-mentioned purpose, the present invention provides the following technical solutions: a microscope dark field illumination system that can be additionally installed includes an objective lens seat, and also includes a mounting seat movably mounted on the objective lens seat, wherein a ring-shaped dark field chamber is coaxially opened inside, an open ring groove is opened at the end of the dark field chamber, a collimating light lens seat is arranged in the dark field chamber, a light focusing seat is arranged at the connection between the dark field chamber and the open ring groove, and an LED lamp bead facing the collimating light lens seat is arranged in the dark field chamber so that light is emitted along the dark field chamber and the open ring groove to form an annular aperture coaxial with the mounting seat.

[0007] Preferably, a fixing piece is symmetrically and slidably provided on the mounting seat, a clamping portion is provided on the fixing piece, the mounting seat is sleeved on the objective lens seat, and the fixing piece is driven to slide together so that the clamping portion is clamped on the top of the objective lens seat, and the fixing piece abuts against the upper end of the objective lens seat to lock the mounting seat on the objective lens seat.

[0008] Preferably, a first sliding groove is provided in the dark field chamber, a first sliding portion is symmetrically provided on the collimating light lens seat, the first sliding portion is slidably provided in the first sliding groove, a mounting portion is symmetrically provided on the mounting seat, an adjustment seat is vertically slidably provided on the mounting portion and is magnetically attracted to the first sliding portion, and the adjustment seat is driven to slide vertically to drive the collimating light lens seat in the dark field chamber to slide relative to the LED lamp bead.

[0009] Preferably, a locking member and an elastic member are symmetrically arranged in the mounting seat, an embedded portion is arranged on the locking member, the fixing member is slidably arranged in a horizontal displacement groove opened on the mounting seat, and two limiting grooves are opened on the fixing member, the elastic member pushes the locking member to slide so that the embedded portion of the locking member is embedded in the limiting groove to lock the fixing member.

[0010] Preferably, a ball handle is provided on the adjustment seat.

[0011] Preferably, a movable groove is provided on the mounting seat, and a paddle portion is provided on the locking member, the paddle portion extends out of the mounting seat through the movable groove, and the locking member is slidably arranged on the mounting seat so that the paddle portion is movable in the movable groove.

[0012] Preferably, it also includes a limit plate, on which a limit circular hole and a clamping groove are provided, and the mounting portion is provided with a clamping portion, and the clamping groove of the limit plate is clamped with the clamping portion so that the limit circular hole is sleeved on the ball handle portion and limits the adjustment seat.

[0013] Preferably, a second sliding groove is provided on the mounting seat, and a second sliding portion is provided on the adjusting seat, and the second sliding portion is slidably disposed in the second sliding groove.

[0014] In the above technical scheme, the present invention provides a microscope dark field illumination system that can be additionally installed, which has the following beneficial effects: the LED lamp beads arranged in the mounting seat can emit light, and the emitted light is emitted from the open ring groove of the dark field chamber through the collimating light lens seat and the light focusing seat to form a coaxial annular aperture located at the lower side of the mounting seat, and the mounting seat can be directly coaxially mounted on the objective lens seat to realize the coaxial annular aperture formed below the objective lens seat for fill light, and the opening and closing of the fill light aperture can be directly realized by controlling the opening and closing of the LED lamp beads, without the need to additionally disassemble the objective lens, which is convenient for actual use and improves observation efficiency; secondly, the mounting seat can be disassembled from the objective lens seat without interfering with the original objective lens seat structure, thereby improving convenience of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0016] Figure 1 A schematic diagram of the overall structure provided for an embodiment of the present invention;

[0017] Figure 2A schematic cross-sectional view of the overall structure provided for an embodiment of the present invention;

[0018] Figure 3 A schematic diagram of the structure of a mounting base and an objective lens base provided in an embodiment of the present invention;

[0019] Figure 4 A schematic cross-sectional view of a structure generally mounted on an objective lens holder provided by an embodiment of the present invention;

[0020] Figure 5 A schematic diagram of an overall explosion structure provided for an embodiment of the present invention.

[0021] Description of reference numerals:

[0022] 1. Mounting seat; 11. Dark field chamber; 111. Open ring groove; 112. First sliding groove; 12. Mounting part; 13. Second sliding groove; 14. Horizontal shift groove; 15. Clamping part; 16. Movable groove; 17. Magnetic power supply part; 2. LED lamp beads; 3. Collimating light lens seat; 31. First sliding part; 32. Light focusing seat; 4. Adjustment seat; 41. Ball handle part; 42. Second sliding part; 5. Fixing part; 51. Clamping part; 52. Limiting groove; 6. Locking part; 61. Embedding part; 62. Paddle part; 7. Elastic part; 8. Limiting plate; 81. Limiting circular hole; 82. Clamping groove; 9. Objective lens seat. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0024] like Figure 1-5 As shown, a microscope dark field illumination system that can be additionally installed includes an objective lens seat 9 and a mounting seat 1 movably mounted on the objective lens seat 9, wherein an annular dark field chamber 11 is coaxially opened inside the objective lens seat 9, an open ring groove 111 is opened at the end of the dark field chamber 11, a collimating light lens seat 3 is arranged in the dark field chamber 11, a light focusing seat 32 is arranged at the connection between the dark field chamber 11 and the open ring groove 111, and an LED lamp bead 2 is arranged in the dark field chamber 11 facing the collimating light lens seat 3 so that light is emitted along the dark field chamber 11 and the open ring groove 111 to form an annular aperture coaxial with the mounting seat 1.

[0025] Specifically, Figure 1As shown, an LED lamp bead 2 is arranged in the mounting base 1, and a magnetic power supply part 17 for supplying power to the LED lamp bead 2 is also arranged on the mounting base 1. The magnetic power supply part 17 can be magnetically attracted to a power supply line to supply power to the LED lamp bead 2. The magnetic power supply part 17 and the power supply line are technical common sense known to those skilled in the art and will not be elaborated here.

[0026] The dark field chamber 11 is coaxially arranged with the mounting seat 1, an open ring groove 111 is provided at the end of the dark field chamber 11, a collimating light lens seat 3 is arranged in the dark field chamber 11, and a light focusing seat 32 is arranged at the connection between the dark field chamber 11 and the open ring groove 111, the LED lamp bead 2 arranged in the mounting seat 1 is turned on to emit light, and the emitted light is emitted from the open ring groove 111 of the dark field chamber 11 through the collimating light lens seat 3 and the light focusing seat 32 to form a coaxial annular aperture located at the lower side of the mounting seat 1, and the mounting seat 1 can be directly coaxially mounted on the objective lens seat 9 to realize the coaxial annular aperture formed below the objective lens seat 9 for fill light, and the opening and closing of the fill light aperture can be directly realized by controlling the opening and closing of the LED lamp bead 2, without the need to additionally disassemble the objective lens, which is convenient for actual use and improves the observation efficiency. Secondly, the mounting seat 1 can be disassembled from the objective lens seat 9 without interfering with the original structure of the objective lens seat 9, thereby improving the convenience of use.

[0027] In the above technical scheme, the LED lamp bead 2 arranged in the mounting seat 1 can emit light, and the emitted light is emitted from the open ring groove 111 of the dark field chamber 11 through the collimating light lens seat 3 and the light focusing seat 32 to form a coaxial annular aperture located at the lower side of the mounting seat 1. The mounting seat 1 can be directly coaxially mounted on the objective lens seat 9 to realize the coaxial annular aperture formed below the objective lens seat 9 for fill light. The opening and closing of the fill light aperture can be directly realized by controlling the opening and closing of the LED lamp bead 2, and there is no need to disassemble the objective lens lens additionally, which is convenient for actual use and improves observation efficiency. Secondly, the mounting seat 1 can be disassembled from the objective lens seat 9 without interfering with the original structure of the objective lens seat 9, thereby improving convenience of use.

[0028] As another embodiment provided by the present invention, a fixing member 5 is symmetrically and slidably arranged on the mounting seat 1, and a clamping portion 51 is arranged on the fixing member 5. The mounting seat 1 is sleeved on the objective lens seat 9, and the fixing member 5 is driven to slide together so that the clamping portion 51 is clamped on the top of the objective lens seat 9, and the fixing member 5 contacts the upper end of the objective lens seat 9 to lock the mounting seat 1 on the objective lens seat 9.

[0029] Specifically, Figure 2As shown, a clamping portion 51 is provided on the fixing member 5, and the fixing member 5 is slidably provided on the mounting seat 1, so that the mounting seat 1 can be sleeved on the objective lens seat 9 first, and then the fixing member 5 is driven to slide close to the upper end neck of the objective lens seat 9, so that the clamping portion 51 of the fixing member 5 is clamped on the neck of the objective lens seat 9, and at this time, the fixing member 5 extends to abut against the upper end of the objective lens seat 9 to lock the mounting seat 1 and the objective lens seat 9 into one, thereby avoiding the problem of the mounting seat 1 shaking or falling relative to the objective lens seat 9, and improving the installation stability between the mounting seat 1 and the objective lens seat 9.

[0030] As another embodiment provided by the present invention, a first sliding groove 112 is opened in the dark field chamber 11, and a first sliding portion 31 is symmetrically arranged on the collimating light lens seat 3, and the first sliding portion 31 is slidably arranged in the first sliding groove 112, and a mounting portion 12 is symmetrically arranged on the mounting seat 1, and an adjustment seat 4 that is magnetically attracted to the first sliding portion 31 is vertically slidably arranged on the mounting portion 12, and the adjustment seat 4 is driven to slide vertically to drive the collimating light lens seat 3 located in the dark field chamber 11 to slide relative to the LED lamp bead 2.

[0031] Specifically, Figure 2 As shown, a first sliding groove 112 is provided in the dark field chamber 11, and a first sliding portion 31 is symmetrically provided on the collimating light lens seat 3. The first sliding portion 31 is slidably provided in the first sliding groove 112, and a mounting portion 12 is symmetrically provided on the outside of the mounting seat 1, and the adjusting seat 4 is vertically slidably provided on the mounting portion 12, and the adjusting seat 4 is magnetically attracted to the first sliding portion 31, and the adjusting seat 4 can be manually pushed to slide vertically to drive the first sliding portion 31 to slide in the first sliding groove 112, at this time, the collimating light lens seat 3 follows the first sliding portion 31 to slide axially in the dark field chamber 11 to move relative to the LED lamp bead 2, when the collimating light lens seat 3 moves closer to the LED lamp bead 2, the LED lamp bead 2 can pass more vertical light through the collimating light lens seat 3, so that the light emitted by the LED lamp bead 2 is refracted from the dark field chamber 11 and the light intensity emitted from the open ring groove 111 increases, thereby increasing the brightness of the coaxial annular aperture formed on the lower side of the mounting seat 1;

[0032] If the adjustment seat 4 is slid to make the collimating light lens seat 3 move further away from the LED lamp bead 2, the LED lamp bead 2 can pass through the collimating light lens seat 3 to direct the vertical light, so that the light emitted by the LED lamp bead 2 is refracted from the dark field chamber 11 and the light intensity emitted from the open ring groove 111 is reduced, thereby reducing the brightness of the coaxial annular aperture formed on the lower side of the mounting seat 1. The first sliding part 31 and the adjustment seat 4 are symmetrically arranged on the collimating light lens seat 3 to adjust the brightness of the coaxial annular aperture formed on the lower side of the mounting seat 1, so as to facilitate the adjustment of the brightness of the aperture according to different required fill light intensities and facilitate practical use.

[0033] As another embodiment provided by the present invention, a locking member 6 and an elastic member 7 are symmetrically arranged in the mounting seat 1, an embedding portion 61 is arranged on the locking member 6, the fixing member 5 is slidably arranged in the horizontal displacement groove 14 opened on the mounting seat 1, and two limiting grooves 52 are opened on the fixing member 5, and the elastic member 7 pushes the locking member 6 to slide so that the embedding portion 61 of the locking member 6 is embedded in the limiting groove 52 to lock the fixing member 5.

[0034] Specifically, Figure 2 As shown, the locking member 6 is vertically slidably arranged in the mounting seat 1, and the elastic member 7 is arranged below the locking member 6 to push the locking member 6 to slide vertically upward and extend into the horizontal displacement groove 14. Two limiting grooves 52 are provided on the fixing member 5. When it is not necessary to fix the mounting seat 1 to the objective lens seat 9, the fixing member 5 slides to retract the clamping portion 51 into the horizontal displacement groove 14. At this time, the limiting groove 52 on the left side is aligned with the embedding portion 61 of the locking member 6. The elastic member 7 pushes the locking member 6 to slide so that the embedding portion 61 is embedded in the limiting groove 52 on the side of the fixing member 5 close to the clamping portion 51, thereby realizing the stable storage of the fixing member 5 in the mounting seat 1, which is convenient for stable storage and placement when not in use.

[0035] When the mounting seat 1 is sleeved on the objective lens seat 9, the fixing member 5 slides in the horizontal displacement groove 14 so that the clamping portion 51 is clamped on the objective lens seat 9. At this time, the limiting groove 52 on the fixing member 5 that is away from the clamping portion 51 is aligned with the embedding portion 61. At this time, the elastic member 7 pushes the locking member 6 to slide so that the embedding portion 61 is embedded in the limiting groove 52 on the side of the fixing member 5 that is away from the clamping portion 51. Then, the locking member 6 is used to complete the stable locking of the fixing member 5, so as to avoid the fixing member 5 from loosening and causing the mounting seat 1 and the objective lens seat 9 to separate or loosen, thereby further improving the assembly stability between the mounting seat 1 and the objective lens seat 9.

[0036] As another embodiment provided by the present invention, a ball handle portion 41 is provided on the adjustment seat 4 .

[0037] Specifically, a ball handle portion 41 is provided on the adjustment seat 4, and the ball handle portion 41 can be used to move the push adjustment seat 4 to adjust the position of the collimating light lens seat 3 to adjust the aperture brightness, which is convenient for actual adjustment.

[0038] As another embodiment provided by the present invention, a movable groove 16 is provided on the mounting seat 1, and a paddle portion 62 is provided on the locking member 6. The paddle portion 62 extends out of the outside of the mounting seat 1 through the movable groove 16, and the locking member 6 is slidably provided on the mounting seat 1 so that the paddle portion 62 is located in the movable groove 16 and moves.

[0039] Specifically, Figure 3As shown, a movable groove 16 is provided on the mounting seat 1, and a paddle portion 62 is provided on the locking member 6. The paddle portion 62 extends out of the mounting seat 1 through the movable groove 16. When the elastic member 7 pushes the embedding portion 61 of the locking member 6 to embed into the limiting groove 52 of the fixing member 5, the paddle portion 62 is located in the movable groove 16 and moves. If the locking of the fixing member 5 is to be contacted, the paddle portion 62 can be used to drive the locking member 6 to slide away from the fixing member 5 to unlock the fixing member 5, thereby realizing the disassembly or installation between the mounting seat 1 and the objective lens seat 9.

[0040] As another embodiment provided by the present invention, it also includes a limit plate 8, on which a limit circular hole 81 and a clamping groove 82 are provided, and a clamping portion 15 is provided on the mounting portion 12. The clamping groove 82 of the limit plate 8 is clamped with the clamping portion 15 so that the limit circular hole 81 is sleeved on the ball handle portion 41 and limits the adjustment seat 4.

[0041] Specifically, Figure 5 As shown, a limiting circular hole 81 is provided in the middle of the limiting plate 8, and a snap-in groove 82 is also provided on the limiting plate 8. When the adjusting seat 4 can be manually pushed to slide vertically to drive the first sliding part 31 to slide in the first sliding groove 112, the collimating light lens seat 3 follows the first sliding part 31 to slide axially in the dark field chamber 11 to move relative to the LED lamp bead 2 to adjust the brightness of the coaxial annular aperture formed on the lower side of the mounting seat 1. The snap-in groove 82 of the limiting plate 8 can be snap-fitted with the snap-in part 15 of the mounting part 12. At this time, the limiting circular hole 81 of the limiting plate 8 is sleeved on the ball handle part 41 and limits the adjusting seat 4, thereby avoiding accidental movement of the adjusting seat 4 after the adjustment is completed, and improving the strength and stability of the aperture.

[0042] As another embodiment provided by the present invention, a second sliding groove 13 is provided on the mounting seat 1 , and a second sliding portion 42 is provided on the adjusting seat 4 . The second sliding portion 42 is slidably disposed in the second sliding groove 13 .

[0043] Specifically, a second sliding groove 13 is provided on the mounting seat 1, and a second sliding portion 42 is provided on the adjusting seat 4. The second sliding portion 42 is slidably arranged in the second sliding groove 13. The second sliding portion 42 and the second sliding groove 13 are utilized to improve the vertical sliding stability of the adjusting seat 4 on the mounting portion 12.

[0044] Working principle:

[0045] First, the mounting seat 1 is sleeved on the objective lens seat 9, and then the fixing member 5 is driven to slide close to the upper neck of the objective lens seat 9, so that the clamping portion 51 of the fixing member 5 is clamped on the neck of the objective lens seat 9, and at this time, the fixing member 5 extends to abut against the upper end of the objective lens seat 9 to lock the mounting seat 1 and the objective lens seat 9 into one body;

[0046] The LED lamp bead 2 disposed in the mounting seat 1 is turned on to emit light, and the emitted light is emitted from the open ring groove 111 of the dark field chamber 11 through the collimating light lens seat 3 and the light focusing seat 32 to form a coaxial annular aperture located at the lower side of the mounting seat 1;

[0047] Subsequently, the adjustment seat 4 is manually pushed to slide vertically to drive the first sliding part 31 to slide in the first sliding groove 112. At this time, the collimated light lens seat 3 follows the first sliding part 31 to slide axially in the dark field chamber 11 to move relative to the LED lamp bead 2 to achieve the adjustment of the brightness of the coaxial annular aperture formed on the lower side of the mounting seat 1. The snap-in groove 82 of the limit plate 8 can be snap-fitted with the snap-in part 15 of the mounting part 12. At this time, the limiting circular hole 81 of the limit plate 8 is sleeved on the ball handle part 41 and limits the adjustment seat 4, thereby avoiding accidental movement of the adjustment seat 4 after the adjustment is completed.

[0048] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A microscope dark field illumination system that can be additionally installed, comprising an objective lens holder (9), characterized in that: It also comprises a mounting seat (1) movably mounted on the objective lens seat (9), wherein a ring-shaped dark field chamber (11) is coaxially provided therein, an open annular groove (111) is provided at the end of the dark field chamber (11), a collimating light lens seat (3) is arranged in the dark field chamber (11), a light focusing seat (32) is arranged at the connection between the dark field chamber (11) and the open annular groove (111), and an LED lamp bead (2) facing the collimating light lens seat (3) is arranged in the dark field chamber (11) so that light is emitted along the dark field chamber (11) and the open annular groove (111) to form an annular aperture coaxial with the mounting seat (1).

2. A microscope dark field illumination system that can be additionally installed according to claim 1, characterized in that: A fixing member (5) is symmetrically slidably arranged on the mounting seat (1), and a clamping portion (51) is arranged on the fixing member (5). The mounting seat (1) is sleeved on the objective lens seat (9), and the fixing member (5) is driven to slide close to each other so that the clamping portion (51) is clamped on the top of the objective lens seat (9), and the fixing member (5) contacts the upper end of the objective lens seat (9) to lock the mounting seat (1) on the objective lens seat (9).

3. A microscope dark field illumination system that can be additionally installed according to claim 2, characterized in that: A first sliding groove (112) is provided in the dark field chamber (11); a first sliding portion (31) is symmetrically provided on the collimating light lens seat (3); the first sliding portion (31) is slidably provided in the first sliding groove (112); a mounting portion (12) is symmetrically provided on the mounting seat (1); an adjusting seat (4) is vertically slidably provided on the mounting portion (12) and is magnetically attracted to the first sliding portion (31); the adjusting seat (4) is driven to slide vertically to drive the collimating light lens seat (3) located in the dark field chamber (11) to slide relative to the LED lamp bead (2).

4. A microscope dark field illumination system that can be additionally installed according to claim 3, characterized in that: A locking member (6) and an elastic member (7) are symmetrically arranged in the mounting seat (1); an embedding portion (61) is arranged on the locking member (6); the fixing member (5) is slidably arranged in a horizontal displacement groove (14) provided on the mounting seat (1); and two limiting grooves (52) are provided on the fixing member (5); the elastic member (7) pushes the locking member (6) to slide so that the embedding portion (61) of the locking member (6) is embedded in the limiting groove (52) to lock the fixing member (5).

5. The microscope dark field illumination system that can be additionally installed according to claim 4, characterized in that: The adjustment seat (4) is provided with a ball handle portion (41).

6. A microscope dark field illumination system that can be additionally installed according to claim 5, characterized in that: The mounting seat (1) is provided with a movable groove (16), the locking member (6) is provided with a paddle portion (62), the paddle portion (62) extends out of the mounting seat (1) through the movable groove (16), and the locking member (6) is slidably arranged on the mounting seat (1) so that the paddle portion (62) is located in the movable groove (16) and moves.

7. The microscope dark field illumination system that can be additionally installed according to claim 6, characterized in that: It also includes a limiting plate (8) on which a limiting circular hole (81) and a clamping groove (82) are provided. The mounting portion (12) is provided with a clamping portion (15). The clamping groove (82) of the limiting plate (8) is clamped with the clamping portion (15) so that the limiting circular hole (81) is sleeved on the ball handle portion (41) and limits the adjustment seat (4).

8. The microscope dark field illumination system that can be additionally installed according to claim 7, characterized in that: The mounting seat (1) is provided with a second sliding groove (13), the adjusting seat (4) is provided with a second sliding portion (42), and the second sliding portion (42) is slidably arranged in the second sliding groove (13).

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