An improved lead frame and method of using the same

Abstract

The present invention discloses an improved lead frame and a method for using the same, comprising a plastic-sealed lead frame body, heat dissipation assemblies provided on both ends of the outer surface of the plastic-sealed lead frame body, support leg assemblies provided on both sides of the outer surface of the plastic-sealed lead frame body, and six sets of support leg assemblies, sockets provided on both ends of the outer surface of the plastic-sealed lead frame body, convex slots provided at the lower portion of the sockets, first slots provided on both sides of the outer surface of the plastic-sealed lead frame body, and limit slots provided on the left and right sides of the first slot, the support leg assemblies including support rods, connecting assemblies, and adjusting assemblies. The improved lead frame and the method for using the same according to the present invention have the advantages of good heat dissipation, easy installation and disassembly between the support legs and the plastic-sealed lead frame body, and easy adjustment of the height of the plastic-sealed lead frame body.

Description

Technical Field

[0001] The present invention relates to the technical field of lead frames, in particular to an improved lead frame and a use method thereof. Background Art

[0002] After the semiconductor chip is packaged, it is connected to the external circuit board through its exposed pins. One end of the external pin extends into the chip packaging area and is connected to the chip through the lead, and the other end extends out of the packaging area and is evenly arranged. Since the pins do not touch each other, the pins are generally bent. In the prior art, a Chinese patent document with authorization announcement number CN204424316U discloses a SOP8 package lead frame for a high-power LED driver chip, including pins, side connecting ribs, a first base island and a second base island, which expands the bearing area of the first base island and has good heat dissipation performance. However, the pins and the main body are not easy to install and disassemble, resulting in pin breakage during transportation. In addition, the height of the plastic-sealed lead frame main body is not easy to adjust, which has certain limitations during installation and has certain adverse effects on people's use. To this end, we propose an improved lead frame and its use method. Summary of the Invention

[0003] (1) Technical problems solved

[0004] In response to the deficiencies in the prior art, the present invention provides an improved lead frame and a method for using the same, which has the advantages of good heat dissipation, easy installation and disassembly between the legs and the plastic lead frame body, and easy adjustment of the height of the plastic lead frame body, and can effectively solve the problems in the background technology.

[0005] (2) Technical solution

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is: an improved lead frame and a method for using the same, comprising a plastic-sealed lead frame body, wherein the outer surfaces at both ends of the plastic-sealed lead frame body are provided with heat dissipation components, the outer surfaces at both sides of the plastic-sealed lead frame body are provided with support leg components, and the number of the support leg components is six groups, the outer surfaces at both ends of the plastic-sealed lead frame body are provided with insertion holes, the lower part of the insertion holes is provided with a convex card slot, the outer surfaces at both sides of the plastic-sealed lead frame body are provided with a first slot, and the left and right sides of the first slot are provided with limiting slots, the support leg assembly includes a support rod, a connecting assembly and an adjustment assembly, and the support rod is detachably connected to the plastic-sealed lead frame body through the connecting assembly, the heat dissipation assembly includes a heat dissipation hole, a heat dissipation fin and a convex card block, and the convex card block is fixedly installed in the middle of the outer surface of one side of the heat dissipation hole, and the heat dissipation hole is provided on the upper and lower sides of the outer surface of the front end of the heat dissipation fin.

[0007] As a preferred technical solution, the outer wall of the convex card block and the insertion hole are in sliding connection, and the outer wall of the convex card block and the convex card slot are in snap connection.

[0008] As a preferred technical solution, the connecting assembly includes a first plug-in block, a pressing block, a threaded hole, a movable groove, a screw, a limit plate, a limit rod, a sliding hole, a first telescopic spring, a first movable cavity and a limit block, and the first movable cavity is opened on the left and right sides of the first plug-in block, the movable groove is opened at one end of the outer surface of both sides of the first plug-in block, the sliding hole is opened at the other end of the outer surface of both sides of the first plug-in block, and the movable groove, the sliding hole and the first movable cavity are communicated with the first plug-in block and the first slot are snap-fitted, the limit rod and the limit groove are snap-fitted, and the outer surface of one end of the first plug-in block is fixedly connected to the outer surface of one end of the support rod.

[0009] As a preferred technical solution, the first telescopic spring and the limit block are both located inside the first movable cavity, the outer surface of one end of the first telescopic spring is fixedly connected to one end of the first movable cavity, the outer surface of the other end of the first telescopic spring is fixedly connected to the outer surface of one side of the limit block, the limit rod is fixedly installed on one end of the outer surface of one side of the limit block, and the pressing block is fixedly installed on the other end of the outer surface of one side of the limit block.

[0010] As a preferred technical solution, one side outer surface of the limit block is elastically connected to one end of the first movable cavity through a first telescopic spring, the limit rod and the sliding hole are slidably connected, and the pressing block and the movable groove are slidably connected.

[0011] As a preferred technical solution, the limiting plate is fixedly mounted on the outer surface of one end of the screw rod, the threaded hole is opened on the outer surface of one end of the pressing block, and the screw rod and the threaded hole are threadedly connected.

[0012] As a preferred technical solution, the adjustment assembly includes a fixed block, a limiting hole, a second telescopic spring, a hemispherical limiting block, a movable rod, a second movable cavity, a second slot and a second plug-in block, and the second slot is opened on the upper end outer surface of the fixed block, and the outer surface of one side of the second plug-in block is fixedly connected to the outer surface of the other end of the support rod. The number of the limiting holes is three groups, and the three groups of limiting holes are opened on the outer surface of one side of the fixed block, and the limiting holes are communicated with the second slot.

[0013] As a preferred technical solution, the second movable cavity is opened at the lower part of the outer surface of one side of the second plug-in block, the second telescopic spring and the movable rod are located inside the second movable cavity, and the hemispherical limit block is fixedly installed on the outer surface of one end of the movable rod.

[0014] As a preferred technical solution, the second plug block is slidably connected to the second slot, the outer surface of one end of the second telescopic spring is fixedly connected to one end of the second movable cavity, the outer surface of the other end of the second telescopic spring is fixedly connected to the outer surface of the other end of the movable rod, the movable rod and the second movable cavity are slidably connected, and the hemispherical limit block and the limit hole are snap-fitted.

[0015] As a preferred method of using the technical solution, the following steps are included:

[0016] S1: First, install the heat dissipation assembly by inserting the convex card block into the socket and then pressing down the heat dissipation fin to make the convex card block engage with the convex card slot, thereby completing the installation of the heat dissipation assembly;

[0017] S2: Then connect the leg assembly to the plastic lead frame body, squeeze the pressing block to compress the first telescopic spring, so that one end of the limit rod enters the sliding hole, then insert the first insert block into the first slot, release the pressing block, so that the limit rod is stuck in the inner part of the limit groove, and then connect it to the threaded hole with a screw to increase stability;

[0018] S3: Finally, adjust the height of the plastic lead frame body by squeezing the hemispherical limit block and pulling the second plug block 32 so that the second plug block slides in the second slot. When the hemispherical limit block reaches the limit hole, the second telescopic spring resets the hemispherical limit block and engages with the limit hole, thereby completing the height adjustment.

[0019] (3) Beneficial effects

[0020] Compared with the prior art, the present invention provides an improved lead frame and a method for using the same, which has the following beneficial effects:

[0021] 1. This improved lead frame and its use method, a heat dissipation assembly is provided at both ends of the plastic sealed lead frame body. When first installing the heat dissipation assembly, a convex card block is inserted into the socket, and then the convex card block is pressed down to make the convex card block and the convex card slot engage, thereby completing the installation of the heat dissipation fins. The heat dissipation fins facilitate the heat dissipation of the heat dissipation assembly, and the heat dissipation holes further enhance the heat dissipation effect.

[0022] 2. This improved lead frame and its use method, in order to facilitate the installation and disassembly between the support leg assembly and the plastic sealed lead frame body, a connecting assembly is set, first squeezing the pressing block, the pressing block slides along the movable groove, the pressing block drives the sliding hole to squeeze the first telescopic spring inside the first movable cavity, the limit block drives the limit rod along the sliding hole, so that the limit rod enters the sliding hole, and then the first plug block is inserted into the first slot, and the pressing block is released. Due to the reset effect of the first telescopic spring, the sliding hole is stuck in the limit groove, thereby completing the installation of the support leg assembly, and then the screw rod is threadedly connected to the threaded hole, which increases stability and facilitates transportation after disassembly, reducing the damage rate.

[0023] 3. This improved lead frame and its use method, in order to adjust the distance between the plastic-sealed lead frame body and the main body to facilitate better heat dissipation, and to facilitate the installation of the plastic-sealed lead frame body according to the installation situation, an adjustment component is provided. By squeezing the hemispherical limit block, the hemispherical limit block drives the movable rod to slide along the second movable cavity, so that the hemispherical limit block enters the second movable cavity, and then pulls the second plug block to make the hemispherical limit block reach another set of limit holes. Due to the reset action of the second telescopic spring, the hemispherical limit block enters the limit hole, thereby completing the adjustment of the height of the plastic-sealed lead frame body. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a schematic diagram of the overall structure of an improved lead frame and its use method of the present invention.

[0025] Figure 2 The present invention is a schematic structural diagram of a plastic-sealed lead frame main body in an improved lead frame and a method for using the same.

[0026] Figure 3 The present invention is a schematic structural diagram of a heat dissipation component in an improved lead frame and a method for using the same.

[0027] Figure 4 The present invention is a schematic structural diagram of a leg assembly in an improved lead frame and a method for using the same.

[0028] Figure 5 The present invention is a schematic structural diagram of a connection component in an improved lead frame and a method for using the same.

[0029] Figure 6 The present invention is a schematic structural diagram of a connection component in an improved lead frame and a method for using the same.

[0030] Figure 7 The present invention is a schematic structural diagram of an adjustment component in an improved lead frame and a method for using the same.

[0031] In the figure: 1. Plastic sealed lead frame body; 2. Heat dissipation assembly; 3. Support leg assembly; 4. Socket; 5. Convex card slot; 6. First slot; 7. Limiting slot; 8. Heat dissipation hole; 9. Heat dissipation fin; 10. Convex card block; 11. Support rod; 12. Connecting assembly; 13. Adjusting assembly; 14. First plug block; 15. Pressing block; 16. Threaded hole; 17. Movable slot; 18. Screw; 19. Limiting plate; 20. Limiting rod; 21. Sliding hole; 22. First telescopic spring; 23. First movable cavity; 24. Limiting block; 25. Fixed block; 26. Limiting hole; 27. Second telescopic spring; 28. Hemispherical limiting block; 29. Movable rod; 30. Second movable cavity; 31. Second slot; 32. Second plug block. DETAILED DESCRIPTION

[0032] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0033] like Figure 1-7 As shown, an improved lead frame and a method of using the same include a plastic-sealed lead frame body 1, heat dissipation components 2 are provided on the outer surfaces of both ends of the plastic-sealed lead frame body 1, support leg components 3 are provided on the outer surfaces of both sides of the plastic-sealed lead frame body 1, and the number of the support leg components 3 is six groups, the outer surfaces of both ends of the plastic-sealed lead frame body 1 are provided with insertion holes 4, the lower part of the insertion holes 4 is provided with a convex card slot 5, the outer surfaces of both sides of the plastic-sealed lead frame body 1 are provided with a first slot 6, and the left and right sides of the first slot 6 are provided with limiting slots 7, the support leg component 3 includes a support rod 11, a connecting component 12 and an adjustment component 13, and the support rod 11 is detachably connected to the plastic-sealed lead frame body 1 through the connecting component 12, the heat dissipation component 2 includes a heat dissipation hole 8, a heat dissipation fin 9 and a convex card block 10, and the convex card block 10 is fixedly installed in the middle of the outer surface of one side of the heat dissipation hole 8, and the heat dissipation hole 8 is provided on the upper and lower sides of the front end outer surface of the heat dissipation fin 9.

[0034] Furthermore, the outer wall of the convex block 10 and the insertion hole 4 are in sliding connection, and the outer wall of the convex block 10 and the convex slot 5 are in snap connection.

[0035] Furthermore, the connecting assembly 12 includes a first plug-in block 14, a pressing block 15, a threaded hole 16, a movable groove 17, a screw 18, a limit plate 19, a limit rod 20, a sliding hole 21, a first telescopic spring 22, a first movable cavity 23 and a limit block 24, and the first movable cavity 23 is opened on the left and right sides of the first plug-in block 14, the movable groove 17 is opened at one end of the outer surface of both sides of the first plug-in block 14, the sliding hole 21 is opened at the other end of the outer surface of both sides of the first plug-in block 14, and the movable groove 17, the sliding hole 21 and the first movable cavity 23 are communicated with each other, the first plug-in block 14 and the first slot 6 are snap-fitted, the limit rod 20 and the limit groove 7 are snap-fitted, and the outer surface of one end of the first plug-in block 14 is fixedly connected to the outer surface of one end of the support rod 11.

[0036] Furthermore, the first telescopic spring 22 and the limit block 24 are both located inside the first movable chamber 23, the outer surface of one end of the first telescopic spring 22 is fixedly connected to one end of the first movable chamber 23, the outer surface of the other end of the first telescopic spring 22 is fixedly connected to the outer surface of one side of the limit block 24, the limit rod 20 is fixedly installed on one end of the outer surface of one side of the limit block 24, and the pressing block 15 is fixedly installed on the other end of the outer surface of one side of the limit block 24.

[0037] Furthermore, the outer surface of one side of the limit block 24 is elastically connected to one end of the first movable cavity 23 through the first telescopic spring 22, the limit rod 20 and the sliding hole 21 are slidingly connected, and the pressing block 15 and the movable groove 17 are slidingly connected.

[0038] Furthermore, the limiting plate 19 is fixedly mounted on the outer surface of one end of the screw rod 18 , the threaded hole 16 is opened on the outer surface of one end of the pressing block 15 , and the screw rod 18 and the threaded hole 16 are threadedly connected.

[0039] Furthermore, the adjustment assembly 13 includes a fixed block 25, a limiting hole 26, a second telescopic spring 27, a hemispherical limiting block 28, a movable rod 29, a second movable cavity 30, a second slot 31 and a second plug block 32, and the second slot 31 is opened on the upper end outer surface of the fixed block 25, and the outer surface of one side of the second plug block 32 is fixedly connected to the outer surface of the other end of the support rod 11. The number of limiting holes 26 is three groups, and the three groups of limiting holes 26 are opened on the outer surface of one side of the fixed block 25, and the limiting holes 26 are communicated with the second slot 31.

[0040] Furthermore, the second movable cavity 30 is opened at the lower part of the outer surface of one side of the second plug block 32, the second telescopic spring 27 and the movable rod 29 are located inside the second movable cavity 30, and the hemispherical limit block 28 is fixedly installed on the outer surface of one end of the movable rod 29.

[0041] Furthermore, the second plug block 32 is slidably connected to the second slot 31, the outer surface of one end of the second telescopic spring 27 is fixedly connected to one end of the second movable chamber 30, the outer surface of the other end of the second telescopic spring 27 is fixedly connected to the outer surface of the other end of the movable rod 29, the movable rod 29 and the second movable chamber 30 are slidably connected, and the hemispherical limit block 28 and the limit hole 26 are snap-fitted.

[0042] Further usage methods include the following steps:

[0043] S1: First, install the heat dissipation assembly 2 by inserting the convex card block 10 into the socket 4 and then pressing down the heat dissipation fin 9 so that the convex card block 10 is engaged with the convex card slot 5, thereby completing the installation of the heat dissipation assembly 2;

[0044] S2: Then, the support leg assembly 3 is connected to the plastic lead frame body 1. By squeezing the pressing block 15, the first telescopic spring 22 is compressed, so that one end of the limiting rod 20 enters the sliding hole 21. Then, the first inserting block 14 is inserted into the first slot 6. The pressing block 15 is released, so that the limiting rod 20 is snapped into the inside of the limiting groove 7. Then, the screw 18 is connected to the threaded hole 16 to increase stability.

[0045] S3: Finally, adjust the height of the plastic lead frame body 1 by squeezing the hemispherical limit block 28 and pulling the second plug block 32 so that the second plug block 32 slides in the second slot 31. When the hemispherical limit block 28 reaches the limit hole 26, the second telescopic spring 27 resets the hemispherical limit block 28 and engages with the limit hole 26, thereby completing the height adjustment.

[0046] How it works

[0047] The heat dissipation components 2 are provided at both ends of the plastic sealed lead frame body 1. When installing the heat dissipation component 2, the convex card block 10 is inserted into the socket 4, and then the convex card block 10 is pressed down to make the convex card block 10 and the convex card slot 5 be clamped, thereby completing the installation of the heat dissipation fins 9. The heat dissipation fins 9 are provided to facilitate the heat dissipation of the heat dissipation component 2, and the heat dissipation effect is further increased through the provided heat dissipation holes 8. In order to facilitate the installation and disassembly between the support leg component 3 and the plastic sealed lead frame body 1, a connecting component 12 is provided. First, the pressing block 15 is squeezed. The pressing block 15 slides along the movable groove 17. The pressing block 15 drives the sliding hole 21 to squeeze the first telescopic spring 22 inside the first movable cavity 23. The limiting block 24 drives the limiting rod 20 along the sliding hole 21 so that the limiting rod 20 enters the sliding hole 21. Then the first plug 14 is inserted into the first slot 6, and the pressing block 1 is released. 5. Due to the reset effect of the first telescopic spring 22, the sliding hole 21 is stuck in the limiting groove 7, thereby completing the installation of the support leg assembly 3, and then the screw 18 is threadedly connected to the threaded hole 16, which increases stability and facilitates transportation after disassembly, reducing the damage rate; in order to adjust the distance between the plastic sealed lead frame body 1 and the main body, facilitate better heat dissipation, and facilitate the installation of the plastic sealed lead frame body 1 according to the installation situation, an adjustment assembly 13 is set, by squeezing the hemispherical limit block 28, the hemispherical limit block 28 drives the movable rod 29 to slide along the second active cavity 30, so that the hemispherical limit block 28 enters the second active cavity 30, and then pulls the second insert block 32, so that the hemispherical limit block 28 reaches another set of limiting holes 26, due to the reset effect of the second telescopic spring 27, the hemispherical limit block 28 enters the limiting hole 26, thereby completing the height adjustment of the plastic sealed lead frame body 1.

[0048] It should be noted that, in this document, relational terms such as first and second (number one, number two), etc., are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "include," "comprise," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "includes a..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0049] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. An improved lead frame, comprising a plastic sealed lead frame body (1), characterized in that: The outer surfaces of both ends of the plastic lead frame body (1) are provided with heat dissipation components (2), the outer surfaces of both sides of the plastic lead frame body (1) are provided with support leg components (3), and the number of the support leg components (3) is six. The outer surfaces of both ends of the plastic lead frame body (1) are provided with insertion holes (4), the lower part of the insertion holes (4) is provided with a convex card slot (5), the outer surfaces of both sides of the plastic lead frame body (1) are provided with a first slot (6), and the left and right sides of the first slot (6) are provided with a The limiting groove (7), the support leg assembly (3) includes a support rod (11), a connecting assembly (12) and an adjusting assembly (13), and the support rod (11) is detachably connected to the plastic lead frame body (1) through the connecting assembly (12), the heat dissipation assembly (2) includes a heat dissipation hole (8), a heat dissipation fin (9) and a convex block (10), and the convex block (10) is fixedly installed in the middle of the outer surface of one side of the heat dissipation hole (8), and the heat dissipation hole (8) is opened on the upper and lower sides of the front outer surface of the heat dissipation fin (9); The connecting assembly (12) includes a first plug-in block (14), a pressing block (15), a threaded hole (16), a movable groove (17), a screw rod (18), a limiting plate (19), a limiting rod (20), a sliding hole (21), a first telescopic spring (22), a first movable cavity (23) and a limiting block (24), and the first movable cavity (23) is opened on the left and right sides of the first plug-in block (14), the movable groove (17) is opened on one end of the outer surface of both sides of the first plug-in block (14), the sliding hole (21) is opened on the other end of the outer surface of both sides of the first plug-in block (14), and the movable groove (17), the sliding hole (21) and the first movable cavity (23) are communicated with each other, the first plug-in block (14) and the first slot (6) are snap-fitted, the limiting rod (20) and the limiting groove (7) are snap-fitted, and the outer surface of one end of the first plug-in block (14) is fixedly connected to the outer surface of one end of the support rod (11); The first telescopic spring (22) and the limiting block (24) are both located inside the first movable cavity (23); the outer surface of one end of the first telescopic spring (22) is fixedly connected to one end of the first movable cavity (23); the outer surface of the other end of the first telescopic spring (22) is fixedly connected to the outer surface of one side of the limiting block (24); the limiting rod (20) is fixedly mounted on one end of the outer surface of one side of the limiting block (24); and the pressing block (15) is fixedly mounted on the other end of the outer surface of one side of the limiting block (24); One side outer surface of the limit block (24) is elastically connected to one end of the first movable cavity (23) via a first telescopic spring (22); the limit rod (20) and the sliding hole (21) are in sliding connection; and the pressing block (15) and the movable groove (17) are in sliding connection; The limiting plate (19) is fixedly mounted on the outer surface of one end of the screw rod (18), the threaded hole (16) is opened on the outer surface of one end of the pressing block (15), and the screw rod (18) and the threaded hole (16) are threadedly connected; The adjustment assembly (13) includes a fixed block (25), a limiting hole (26), a second telescopic spring (27), a hemispherical limiting block (28), a movable rod (29), a second movable cavity (30), a second slot (31) and a second plug block (32), and the second slot (31) is opened on the outer surface of the upper end of the fixed block (25), and the outer surface of one side of the second plug block (32) is fixedly connected to the outer surface of the other end of the support rod (11), and the number of the limiting holes (26) is three groups, and the three groups of limiting holes (26) are opened on the outer surface of one side of the fixed block (25), and the limiting holes (26) are communicated with the second slot (31); The second movable cavity (30) is opened at the lower part of the outer surface of one side of the second plug block (32), the second telescopic spring (27) and the movable rod (29) are located inside the second movable cavity (30), and the hemispherical limit block (28) is fixedly installed on the outer surface of one end of the movable rod (29); The second plug block (32) is slidably connected to the second slot (31), the outer surface of one end of the second telescopic spring (27) is fixedly connected to one end of the second movable cavity (30), the outer surface of the other end of the second telescopic spring (27) is fixedly connected to the outer surface of the other end of the movable rod (29), the movable rod (29) and the second movable cavity (30) are slidably connected, and the hemispherical limiting block (28) and the limiting hole (26) are snap-fitted.

2. The improved lead frame according to claim 1, characterized in that: The outer wall of the convex card block (10) and the insertion hole (4) are in sliding connection, and the outer wall of the convex card block (10) and the convex card slot (5) are in snap connection.

3. A method for using an improved lead frame according to any one of claims 1-2, characterized in that: The following steps are included: S1: First, install the heat dissipation assembly (2) by inserting the convex card block (10) into the socket (4), and then pressing down the heat dissipation fin (9) so that the convex card block (10) and the convex card slot (5) are engaged, thereby completing the installation of the heat dissipation assembly (2); S2: Then connect the support leg assembly (3) with the plastic lead frame body (1), squeeze the pressing block (15) to compress the first telescopic spring (22), so that one end of the limiting rod (20) enters the sliding hole (21), and then insert the first plug block (14) into the first slot (6), release the pressing block (15), so that the limiting rod (20) is stuck in the inside of the limiting groove (7), and then connect it with the threaded hole (16) through the screw rod (18) to increase stability; S3: Finally, the height of the plastic lead frame body (1) is adjusted by squeezing the hemispherical limiting block (28) and pulling the second plug block (32) so that the second plug block (32) slides in the second slot (31). When the hemispherical limiting block (28) reaches the limiting hole (26), the hemispherical limiting block (28) is engaged with the limiting hole (26) due to the reset action of the second telescopic spring (27), thereby completing the height adjustment.

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