Multi-color three-dimensional heat transfer printing processing equipment for automobile key shell

Abstract

The invention discloses multi-color three-dimensional heat transfer printing machining equipment for an automobile key shell. The multi-color three-dimensional heat transfer printing machining equipment comprises a conveying frame, a heat transfer printing mechanism and a waste gas channel. The retaining assembly comprises a retaining seat, a retaining piece and a movable piece. The multi-color three-dimensional heat transfer printing machining equipment for the automobile key shell is compact in structure and ingenious in design, when the filter base is installed, the filter base only needs to be directly inserted into a waste gas channel and pressed under stress, the first elastic piece and the second elastic piece are kept compressed during pressing, the movable piece and the keeping piece are guided upwards by a certain distance, and then the filter base is installed. And the locking end enters the locking opening to limit the position of the filter seat. The filter seat can be disassembled and assembled without any tool, the workload can be reduced, the operation difficulty can be reduced, the stable installation of the filter seat is realized, and the speed of replacing the filter piece is improved.

Description

Technical Field

[0001] The invention relates to a heat transfer technology, and in particular to a multi-color three-dimensional heat transfer processing device for a car key shell. Background Art

[0002] With the continuous advancement of the automotive industry, people's pursuit of an ideal life is also improving. Car keys are one example of this. Wrapping a car key in a key shell can enhance the key's aesthetics. During the processing of car key shells, it is necessary to create a pattern on the surface or customize the pattern according to customer needs, which requires the use of thermal transfer equipment. Thermal transfer equipment prints any image, such as a portrait or landscape, on plain paper or high-precision printing paper using thermal transfer ink. Then, heating it to a certain temperature, the image on the paper is transferred to plastic, porcelain cups, plates, tiles, clothing, metal, and other materials with realistic colors.

[0003] Thermal transfer equipment heats the ink during the thermal transfer process, which produces some harmful gases. Long-term work near the thermal transfer machine will cause certain damage to the health of workers. Exhaust gas treatment requires the exhaust gas to be absorbed and filtered, so the filter element needs to be replaced regularly. Currently, the filter element is fixed with bolts, which will wear out after long-term use. It is also inconvenient to disassemble and assemble, requiring special tools. Summary of the Invention

[0004] In order to solve the defects of the above-mentioned prior art, the present invention proposes a multi-color three-dimensional thermal transfer processing equipment for a car key shell.

[0005] The technical solution of the present invention is achieved as follows:

[0006] A multi-color three-dimensional thermal transfer processing device for a car key shell, comprising:

[0007] a conveying rack, the conveying rack being used to convey key shells to be processed;

[0008] A heat transfer mechanism is provided above the conveying frame, and is used to perform heat transfer processing on the surface of the key housing passing through;

[0009] And an exhaust gas channel installed at the upper end of the thermal transfer mechanism, an air collecting chamber is provided at the lower end of the exhaust gas channel, a filter seat is provided in the middle of the exhaust gas channel, and a filter element is provided in the middle of the filter seat, wherein

[0010] A symmetrically arranged sliding seat is provided inside the exhaust gas channel, a sliding channel is formed in the middle of the sliding seat, a locking plate and a symmetrically arranged sliding plate are provided on the filter seat, the sliding plate is provided in the sliding channel, and a retaining assembly that cooperates with the locking plate is provided on the exhaust gas channel, the retaining assembly comprising:

[0011] A retaining seat, wherein a limiting sliding groove is provided in the middle of the retaining seat;

[0012] A retaining member installed in the limiting slide groove, wherein the retaining member is connected to the retaining seat by bolts, a locking end is provided at the lower end of the retaining member for cooperating with the locking plate, and a movable area is formed in the middle of the retaining member;

[0013] And a movable part installed in the movable area, the movable part cooperates with the sliding seat to limit the position, a first elastic part is provided between the movable part and the inner wall of the movable area, and a second elastic part is provided between the upper end of the retaining part and the retaining seat.

[0014] In the present invention, the retaining seat is provided with a strip hole, the retaining member is provided with a threaded hole, the strip hole is arranged in the limiting sliding groove, and the bolt is provided with a threaded portion that cooperates with the threaded hole.

[0015] In the present invention, a T-shaped block is provided on the sliding seat, and a T-shaped groove matched with the T-shaped block is provided on the inner wall of the exhaust gas channel.

[0016] In the present invention, a first baffle and a second baffle are further provided on the sliding seat, the sliding channel is formed between the first baffle and the second baffle, the first baffle is arranged at the upper end of the second baffle, and the first baffle is provided with a first triangular guide at one end facing the retaining assembly, and a first guide slope and a blocking block are provided above the first triangular guide.

[0017] In the present invention, a second triangular guide is provided at one end of the sliding plate facing the holding assembly, and a second guide slope parallel to the first guide slope is provided at the upper end of the second triangular guide.

[0018] In the present invention, the movable part is composed of a first movable body and a second movable body, the height of the first movable body is greater than the height of the second movable body, the first movable body is provided with a first positioning hole that cooperates with the first elastic part, and the second movable body is provided with a third triangular guide and a guide end that cooperate with the first triangular guide and the second triangular guide, and a guide gap is formed between the third triangular guide and the guide end.

[0019] In the present invention, a third guiding slope is provided on the third triangular guide, and the third guiding slope is arranged parallel to the first guiding slope and the second guiding slope. A fourth guiding slope is provided on the guiding end.

[0020] In the present invention, the retaining member is composed of an upper limit block, a limiting body and a lower limit block. The upper limit block is provided with a second positioning hole that cooperates with the second elastic member. The middle of the limiting body forms the active area. The limiting body is provided with symmetrical limiting extensions, and a movable opening is formed between the limiting extensions. The first movable body is arranged in the active area, and the second movable body is arranged in the movable opening.

[0021] In the present invention, the lower end of the lower limit block is provided with a vertical section and a transverse section, the locking end is arranged on the transverse section, a accommodating area is formed between the vertical section and the locking end, an avoidance opening is formed between the locking end and the lower limit block, and a fifth guide slope is provided on the locking end.

[0022] In the present invention, the locking plate is provided with an accommodating opening cooperating with the lower limit block, the lower end surface of the locking plate is provided with a locking opening cooperating with the locking section, and the locking opening is provided with a sixth guide slope cooperating with the fifth guide slope.

[0023] The multi-color, three-dimensional thermal transfer printing equipment for automobile key housings embodying the present invention has the following beneficial effects: It has a compact structure and an ingenious design. When installing the filter seat, the filter seat simply needs to be inserted directly into the exhaust passage, pressed against it, and the first and second elastic members kept compressed during the pressing process. The movable member and retaining member are then guided upward a certain distance, allowing the locking end to enter the locking opening and restrict the position of the filter seat. This not only allows the filter seat to be disassembled and assembled without any tools, but also reduces workload and operational difficulty, enabling stable installation of the filter seat and increasing the speed of filter replacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic structural diagram of the multi-color three-dimensional thermal transfer processing equipment for a car key shell of the present invention;

[0025] Figure 2 for Figure 1 Schematic diagram of the exhaust gas channel structure;

[0026] Figure 3 for Figure 2 Exploded diagram;

[0027] Figure 4 for Figure 3 Schematic diagram of the filter seat structure;

[0028] Figure 5 for Figure 4 A schematic diagram of the structure in another direction;

[0029] Figure 6 for Figure 5 A local enlarged view of point A in FIG;

[0030] Figure 7 for Figure 3 Schematic diagram of the sliding seat structure;

[0031] Figure 8 for Figure 7 A schematic diagram of the structure in another direction;

[0032] Figure 9 for Figure 3 Schematic diagram of the retaining component structure in FIG;

[0033] Figure 10 for Figure 9 The main view;

[0034] Figure 11 for Figure 9 Exploded diagram;

[0035] Figure 12 for Figure 11 Schematic diagram of the structure of the moving parts;

[0036] Figure 13 This is a schematic diagram of the installation state of the retaining assembly and the filter seat structure in the present invention;

[0037] Figure 14 It is the main perspective view of 13;

[0038] Figure 15 for Figure 14 A partial enlarged view of point B in FIG.

[0039] In the figure: conveyor frame 1, thermal transfer mechanism 2, exhaust gas channel 3, filter seat 4, gas collection chamber 5, first plate 6, second plate 7, third plate 8, fourth plate 9, gap 10, locking plate 11, positioning port 12, sliding seat 13, blocking block 14, insertion port 15, locking end 16, holding seat 17, sliding channel 18, T-block 19, T-slot 20, first baffle 21, second baffle 22, holding assembly 23, first triangular guide 24, first guide slope 25, second triangular guide 26, first elastic member 27, second elastic member 28, third triangular guide 29, movable member 30, second guide slope 31, holding member 3 2. Locking mouth 33, sliding plate 34, limiting sliding groove 35, bolt 36, movable area 37, strip hole 38, threaded hole 39, threaded portion 40, first movable body 41, second movable body 42, first positioning hole 43, guide end 44, guide notch 45, third guide slope 46, fourth guide slope 47, upper limit block 48, limiting body 49, lower limit block 50, second positioning hole 51, limited extension 52, movable mouth 53, vertical section 54, horizontal section 55, accommodating area 56, avoidance mouth 57, fifth guide slope 58, accommodating mouth 59, sixth guide slope 60, top plate 61, fixed plate 62, compression gap 63. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0041] like Figures 1 to 15 As shown, the multi-color 3D thermal transfer processing equipment for automobile key shells of the present invention includes a conveyor frame 1, a thermal transfer mechanism 2, and an exhaust duct 3. The conveyor frame 1 is used to transport key shells to be processed. Of course, a base that cooperates with the key shells can be provided on the conveyor belt of the conveyor frame 1 to limit the position of the key shells, thereby ensuring that the key shells do not shift during movement and ensuring the accuracy of the thermal transfer.

[0042] The heat transfer mechanism 2 is arranged above the conveying frame 1 and is used to perform heat transfer processing on the surface of the key shell passing through. The heat transfer mechanism 2 will not be described in detail here and the existing technology can be used.

[0043] The exhaust duct 3, mounted at the upper end of the thermal transfer mechanism 2, is used to collect harmful gases generated during operation by the thermal transfer mechanism 2 and filter them through a filter holder 4 disposed in the middle of the exhaust duct 3. A gas collecting bin 5 is disposed at the lower end of the exhaust duct 3, and a filter holder 4 is disposed in the middle of the exhaust duct 3. A filter element (not shown) is disposed in the middle of the filter holder 4. An exhaust fan can be disposed at the upper end of the exhaust duct 3 to extract gas from the lower end of the gas collecting bin 5, allowing all harmful gases to be drawn into the exhaust duct 3 for filtration.

[0044] The exhaust gas channel 3 is composed of a first plate 6, a second plate 7, a third plate 8 and a symmetrically arranged fourth plate 9. The first plate 6 is arranged at one end of the fourth plate 9, and the second plate 7 and the third plate 8 are arranged at the other end of the fourth plate 9. The second plate 7 is arranged at the upper end of the third plate 8. A gap 10 is formed between the second plate 7 and the third plate 8, and the gap 10 is used for the insertion of the locking plate 11.

[0045] At the same time, a symmetrical positioning hole 12 is provided on the second plate 7, and the positioning hole 12 cooperates with the sliding seat 13 so that the sliding seat 13 can be restricted in the positioning hole 12. And because the sliding seat 13 is provided with a blocking block 14, the position of the sliding seat 13 can be limited in conjunction with the second plate 7.

[0046] The first plate 6 is provided with an insertion port 15 that cooperates with the filter seat 4. When the filter element in the middle of the filter seat 4 needs to be replaced, it is only necessary to press and push the filter seat 4 in the direction of the retaining assembly 23 to separate the locking plate 11 from the locking end 16, so that the filter seat 4 is no longer restricted by the retaining seat 17 and the filter seat 4 can be taken out.

[0047] A symmetrically arranged sliding seat 13 is provided inside the exhaust gas channel 3 , and a sliding channel 18 is formed in the middle of the sliding seat 13 . The sliding channel 18 is used for the sliding of the filter seat 4 , so that the sliding seat 13 can carry the filter seat 4 and suspend the filter seat 4 in the exhaust gas channel 3 .

[0048] The sliding seat 13 is provided with a T-block 19, and the inner wall of the exhaust passage 3 is provided with a T-slot 20 that mates with the T-block 19. The T-block 19 and the T-slot 20 cooperate to install the sliding seat 13. The T-slot 20 is provided on the symmetrically arranged fourth plate 9, and the sliding seat 13 is provided with a stopper 14, so the sliding seat 13 can be restrained by the second plate 7.

[0049] The sliding seat 13 is further provided with a first baffle 21 and a second baffle 22, forming a sliding channel 18 therebetween. The first baffle 21 is disposed above the second baffle 22. A first triangular guide 24 is provided at one end of the first baffle 21 facing the retaining assembly 23. A first guide slope 25 and a stop block 14 are provided above the first triangular guide 24.

[0050] The second triangular guide 26 is used to push the movable part 30, so that the movable part 30 is forced to squeeze the first elastic part 27 and the second elastic part 28, and at the same time pushes the third triangular guide 29 on the movable part 30 so that it no longer contacts the first triangular guide 24. Under the push of the second guide inclined surface 31 on the second triangular guide 26, the third triangular guide 29 drives the movable part 30 to move upward, and keeps the third triangular guide 29 in contact with the first triangular guide 24, so that the movable part 30 drives the retaining part 32 to move upward, and the retaining part 32 and the movable part 30 move up a distance as a whole, so that the locking end 16 enters the locking mouth 33.

[0051] The filter seat 4 is provided with a locking plate 11 and a symmetrically arranged sliding plate 34, which is arranged in the sliding channel 18. The sliding plate 34 is provided with a second triangular guide 26 at one end facing the holding assembly 23, and a second guide slope 31 is provided at the upper end of the second triangular guide 26 and is arranged parallel to the first guide slope 25.

[0052] The exhaust passage 3 is provided with a retaining assembly 23 that cooperates with the locking plate 11. The retaining assembly 23 includes a retaining seat 17, a retaining member 32, and a movable member 30. The retaining member 32 is mounted on the retaining seat 17 and can slide on the retaining seat 17, while the movable member 30 is mounted in the middle of the retaining member 32 and can also slide in the middle of the retaining member 32.

[0053] A limiting slot 35 is provided in the middle of the retaining seat 17 , and the retaining member 32 is arranged in the limiting slot 35 . The height of the limiting slot 35 is greater than the height of the limiting body 49 on the retaining member 32 , so that the retaining member 32 can slide in the limiting slot 35 .

[0054] A top plate 61 and a fixing plate 62 are provided on the retaining seat 17 , and a compression gap 63 is formed between the top plate 61 and the upper limit block 48 .

[0055] Retainer 32 is mounted within retaining slot 35 and connected to retaining base 17 via bolt 36. The lower end of retainer 32 is provided with a locking end 16 that engages with locking plate 11, and a movable area 37 is formed in the center of retainer 32. Retaining base 17 has a strip-shaped hole 38, and retainer 32 has a threaded hole 39. Strip-shaped hole 38 is located within retaining slot 35, and bolt 36 has a threaded portion 40 that engages with threaded hole 39. This allows bolt 36 to move with retainer 32, but bolt 36 can move within strip-shaped hole 38 without being restricted by retaining base 17.

[0056] The movable member 30 is installed in the movable area 37 and cooperates with the sliding seat 13 to limit the position. A first elastic member 27 is provided between the movable member 30 and the inner wall of the movable area 37, and a second elastic member 28 is provided between the upper end of the retaining member 32 and the retaining seat 17.

[0057] The movable member 30 consists of a first movable body 41 and a second movable body 42. The first movable body 41 is taller than the second movable body 42. The first movable body 41 is provided with a first positioning hole 43 that mates with the first elastic member 27. Both the first and second elastic members 27 and 28 are springs. The second movable body 42 is provided with a third triangular guide 29 that mates with the first and second triangular guides 24 and 26, and a guide end 44. A guide notch 45 is formed between the third triangular guide 29 and the guide end 44.

[0058] A third guiding slope 46 is provided on the third triangular guide 29 . The third guiding slope 46 is arranged parallel to the first guiding slope 25 and the second guiding slope 31 . A fourth guiding slope 47 is provided on the guiding end 44 .

[0059] The second triangular guide 26 is used to push the third triangular guide 29, causing it to move and maintain contact with the first triangular guide 24. The second triangular guide 26 can also push the third triangular guide 29 away from the first triangular guide 24. When the third triangular guide 29 is within the sliding channel 18 and in contact with the second triangular guide 26, the second elastic member 28 is in a natural state, pushing the movable member 30 to the lower end of the movable area 37. When the third triangular guide 29 is in contact with the first triangular guide 24, the second elastic member 28 is compressed, and the locking end 16 is within the locking opening 33.

[0060] The retaining member 32 comprises an upper stopper 48, a limiting body 49, and a lower stopper 50. The upper stopper 48 is provided with a second positioning hole 51 that engages with the second elastic member 28. The center of the limiting body 49 forms the movable region 37. The limiting body 49 is provided with symmetrical limiting extensions 52. A movable opening 53 is formed between the limiting extensions 52. The first movable body 41 is disposed within the movable region 37, and the second movable body 42 is disposed within the movable opening 53.

[0061] The lower end of the lower limit block 50 is provided with a vertical section 54 and a transverse section 55, the locking end 16 is arranged on the transverse section 55, a receiving area 56 is formed between the vertical section 54 and the locking end 16, an avoidance opening 57 is formed between the locking end 16 and the lower limit block 50, and a fifth guide slope 58 is provided on the locking end 16.

[0062] The locking plate 11 is provided with an accommodating opening 59 that cooperates with the lower limit block 50 , and the lower end surface of the locking plate 11 is provided with a locking opening 33 that cooperates with the locking end 16 . The locking opening 33 is provided with a sixth guide inclined surface 60 that cooperates with the fifth guide inclined surface 58 .

[0063] Since the fifth guide slope 58 and the sixth guide slope 60 are arranged in parallel, when unlocking is required, it is only necessary to push the filter seat 4 toward the retaining assembly 23. The sixth guide slope 60 cooperates with the fifth guide slope 58 to push the retaining member 32 downward, and at this time, the second triangular guide 26 on the sliding plate 34 can also push the movable member 30, so that the movable member 30 compresses the first elastic member 27, while keeping the third triangular guide 29 gradually separated from the first triangular guide 24, and as the retaining member 32 moves downward, the movable member 30 gradually disengages from the contact with the first triangular guide 24, and the locking end 16 disengages from the locking port 33, so that the filter seat 4 is in a position as shown in FIG. Figure 15 The status shown.

[0064] like Figure 15As shown, the state at this time may also be a state that requires locking, and the filter seat 4 is installed in the exhaust gas channel 3. During installation, it is only necessary to push the filter seat 4 toward the retaining assembly 23, so that the sliding plate 34 pushes the movable member 30, keeping the first elastic member 27 compressed, so that the upper surface of the third triangular guide 29 is separated from the lower surface of the first triangular guide 24 and in contact. At this time, the first guide slope 25 on the first triangular guide 24 and the third guide slope 46 on the third triangular guide 29 are on the same slope. Under the restoring elastic force of the first elastic member 27, the third guide slope 46 is guided by the first guide slope 25, and the third triangular guide 29 is guided onto the first triangular guide 24, thereby causing the movable member 30 to move upward for a distance.

[0065] like Figure 15 As shown, the vertical section 54 is now exactly within the accommodating opening 59 on the locking plate 11, and the locking end 16 and the transverse section 55 are at the lower end of the accommodating opening 59. The locking opening 33 is now exactly above the locking end 16, and the distance between the inner wall of the accommodating opening 59 and the vertical section 54 is exactly the same as the accommodating area 56. When the filter holder 4 is pushed further toward the retaining assembly 23, the sliding plate 34 pushes the third triangular guide 29, causing the inner wall of the accommodating opening 59 to contact the vertical plate, keeping the locking opening 33 at the upper end of the accommodating area 56. After releasing the filter holder 4, the elastic force of the first elastic member 27 pushes the movable member 30 onto the first triangular guide 24, causing the retaining member 32 to move upward a distance along with the movable member 30, keeping the second elastic member 28 compressed and the locking end 16 entering the locking opening 33 to confine the filter holder 4.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-color three-dimensional thermal transfer processing equipment for automobile key shells, characterized in that: include: a conveying rack, the conveying rack being used to convey key shells to be processed; A heat transfer mechanism is provided above the conveying frame, and is used to perform heat transfer processing on the surface of the key housing passing through; And an exhaust gas channel installed at the upper end of the thermal transfer mechanism, an air collecting bin is provided at the lower end of the exhaust gas channel, a filter seat is provided in the middle of the exhaust gas channel, a filter element is provided in the middle of the filter seat, a symmetrically arranged sliding seat is provided inside the exhaust gas channel, a sliding channel is formed in the middle of the sliding seat, a locking plate and a symmetrically arranged sliding plate are provided on the filter seat, the sliding plate is provided in the sliding channel, a retaining assembly that cooperates with the locking plate is provided on the exhaust gas channel, and the retaining assembly includes: A retaining seat, wherein a limiting sliding groove is provided in the middle of the retaining seat; A retaining member installed in the limiting slide groove, wherein the retaining member is connected to the retaining seat by bolts, a locking end is provided at the lower end of the retaining member for cooperating with the locking plate, and a movable area is formed in the middle of the retaining member; And a movable part installed in the movable area, the movable part cooperates with the sliding seat to limit the position, a first elastic part is provided between the movable part and the inner wall of the movable area, and a second elastic part is provided between the upper end of the retaining part and the retaining seat.

2. The multi-color three-dimensional thermal transfer processing equipment for automobile key shells according to claim 1 is characterized in that: The retaining seat is provided with a strip hole, the retaining member is provided with a threaded hole, the strip hole is arranged in the limiting sliding groove, and the bolt is provided with a threaded portion that matches the threaded hole.

3. The multi-color 3D thermal transfer processing equipment for automobile key shells according to claim 1, characterized in that: The sliding seat is provided with a T-shaped block, and the inner wall of the exhaust gas channel is provided with a T-shaped groove matched with the T-shaped block.

4. The multi-color three-dimensional thermal transfer processing equipment for automobile key shells according to claim 3, characterized in that: The sliding seat is also provided with a first baffle and a second baffle, the sliding channel is formed between the first baffle and the second baffle, the first baffle is arranged at the upper end of the second baffle, and the first baffle is provided with a first triangular guide at one end facing the retaining assembly, and a first guide slope and a blocking block are provided above the first triangular guide.

5. The multi-color three-dimensional thermal transfer processing equipment for automobile key shells according to claim 4, characterized in that: A second triangular guide is provided at one end of the sliding plate facing the holding assembly, and a second guiding inclined surface is provided at the upper end of the second triangular guide in parallel with the first guiding inclined surface.

6. The multi-color three-dimensional thermal transfer processing equipment for automobile key shells according to claim 5, characterized in that: The movable part is composed of a first movable body and a second movable body. The height of the first movable body is greater than that of the second movable body. The first movable body is provided with a first positioning hole that cooperates with the first elastic part. The second movable body is provided with a third triangular guide and a guide end that cooperate with the first triangular guide and the second triangular guide. A guide gap is formed between the third triangular guide and the guide end.

7. The multi-color three-dimensional thermal transfer processing equipment for automobile key shells according to claim 6, characterized in that: The third triangular guide is provided with a third guiding slope, and the third guiding slope is arranged in parallel with the first guiding slope and the second guiding slope. The guiding end is provided with a fourth guiding slope.

8. The multi-color three-dimensional thermal transfer processing equipment for automobile key shells according to claim 7, characterized in that: The retaining member is composed of an upper limit block, a limiting body and a lower limit block. The upper limit block is provided with a second positioning hole that cooperates with the second elastic member. The middle of the limiting body forms the active area. The limiting body is provided with symmetrical limiting extensions, and a movable opening is formed between the limiting extensions. The first movable body is arranged in the active area, and the second movable body is arranged in the movable opening.

9. The multi-color 3D thermal transfer processing equipment for automobile key shells according to claim 8, characterized in that: The lower end of the lower limit block is provided with a vertical section and a transverse section, the locking end is arranged on the transverse section, a accommodating area is formed between the vertical section and the locking end, an avoidance opening is formed between the locking end and the lower limit block, and a fifth guide slope is provided on the locking end.

10. The multi-color three-dimensional thermal transfer processing equipment for automobile key shells according to claim 9, characterized in that: The locking plate is provided with an accommodating opening that cooperates with the lower limit block, the lower end surface of the locking plate is provided with a locking opening that cooperates with the locking section, and a sixth guiding inclined surface that cooperates with the fifth guiding inclined surface is provided in the locking opening.

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