Plastic packaging bag sealing equipment

Abstract

The invention discloses plastic packaging bag sealing equipment which comprises a workbench, a sealing machine body is mounted above the workbench, a detection mechanism is arranged on the sealing machine body, a protective cover is detachably connected to the sealing machine body, and a mounting mechanism is arranged between the protective cover and the sealing machine body. And a placing mechanism is arranged above the workbench. According to the scheme, the first driving part is started, the telescopic end of the first driving part drives the vacuum box to move downwards, after the vacuum box moves downwards till the sealing ring tightly abuts against a conveying belt of conveying equipment, the second driving part is started, the telescopic end of the second driving part drives the fixing frame to fix a packaging bag, then the vacuum pump is started, and gas in the vacuum box is pumped away through the connecting pipe; the state of the packaging bag is observed by means of the camera, if gas in the bag is pumped away, it is indicated that sealing of the packaging bag is unqualified, and efficient detection of the sealed packaging bag is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of sealing equipment, and specifically to a plastic packaging bag sealing equipment. Background Art

[0002] Sealing equipment is a key piece of equipment in the plastic packaging production process. Its main function is to seal various plastic packaging bags to meet the packaging and preservation requirements of products. It uses technical means such as heat sealing and pressure sealing to make the opening parts of plastic packaging bags fit tightly to form a sealed space.

[0003] In the traditional sealing machine during sealing production, after the packaging bags are sealed by the sealing machine, they directly fall into the collection containers. Only manual random sampling inspection is carried out, which is inconvenient for quickly detecting sealing quality problems, resulting in unqualified products being easily mixed into subsequent processes, seriously affecting the overall quality of products.

[0004] Moreover, for key components such as the heating block and printing wheel inside the sealing machine, when they malfunction or need to be cleaned and maintained after long-term use, the protective cover needs to be removed from the sealing machine. After the protective cover no longer shields these components, maintenance can be carried out. Since the protective cover is installed with bolts, operators need to use a variety of tools and spend a lot of time removing the protective cover, reducing the maintenance efficiency of the equipment.

[0005] At the same time, when the unsealed packaging bags are placed in the placement containers, when a part of the packaging bags are taken, the remaining packaging bags are prone to tipping and stacking. The tipped packaging bags will hinder the normal taking process, reducing the working efficiency of operators. Moreover, products are likely to slip out of the tipped packaging bags, requiring operators to bag them again, affecting the sealing efficiency. Summary of the Invention

[0006] The purpose of the present invention is to provide a plastic packaging bag sealing equipment to solve the problems raised in the above background art.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A plastic packaging bag sealing equipment, including a workbench, a sealing machine body is installed above the workbench, a detection mechanism is provided on the sealing machine body, a protective cover is detachably connected to the sealing machine body, an installation mechanism is provided between the protective cover and the sealing machine body, and a placement mechanism is provided above the workbench.

[0009] The detection mechanism includes a conveying device fixedly connected to the sealing machine body. A mounting plate is fixedly connected to the side of the conveying device. A first driving member is installed in the mounting plate. A vacuum box is installed at the driving end of the first driving member. A sealing ring is installed at the bottom of the vacuum box. A vacuum pump is installed above the vacuum box. A connecting pipe is installed at the suction port of the vacuum pump, and the other end of the connecting pipe is fixedly connected to the vacuum box. A second driving member is installed inside the vacuum box. A fixing frame is installed at the driving end of the second driving member. A camera is installed inside the vacuum box. A guiding plate is installed on the conveying device through a mounting assembly.

[0010] In order to quickly and accurately separate unqualified products, as a preferred solution of the present invention, a third driving member is installed at the bottom of the mounting plate. A pushing plate is installed at the driving end of the third driving member. A guiding rod is installed on the pushing plate, and the guiding rod is slidably connected to the mounting plate.

[0011] In order to keep the conveying device running stably under different working conditions, as a preferred solution of the present invention, the conveying device is supported by a supporting mechanism. The supporting mechanism includes a guiding frame fixedly connected to the bottom of the conveying device. A connecting plate is slidably connected in the guiding frame. Supporting legs are fixedly connected to both sides of the connecting plate.

[0012] In order to facilitate the adjustment of the supporting legs, as a preferred solution of the present invention, a lead screw is rotatably connected in the guiding frame. The connecting plate is threadedly connected to the lead screw. A rotating block is fixedly connected to the bottom end of the lead screw.

[0013] In order to enable the protective cover to be quickly disassembled and installed, as a preferred solution of the present invention, the installation mechanism includes a mounting block fixedly connected to the sealing machine body. A mounting shaft is rotatably connected to the mounting block. A blocking block is fixedly connected to the mounting shaft. A torsion spring is fixedly connected between the mounting shaft and the mounting block. A positioning block is fixedly connected above the protective cover, and the positioning block is inserted into the mounting block.

[0014] In order to make the locking of the protective cover more reliable and ensure convenient operation, as a preferred solution of the present invention, a holding rod is slidably connected in the blocking block. A limiting block is fixedly connected to the holding rod, and the limiting block is slidably connected to the blocking block. A limiting groove is provided on the mounting block.

[0015] In order to enable the packaging bags to be placed in an orderly manner and facilitate the rapid access by the operator, as a preferred embodiment of the present invention, the placement mechanism includes a placement frame installed above the workbench. A plurality of anti - toppling plates are slidably connected in the placement frame. Two guide sleeves are fixedly connected to the anti - toppling plate. A connecting rod is slidably connected in the guide sleeve. Two fixing rods are fixedly connected to the placement frame. A plurality of fixing holes are provided on the fixing rods, and the connecting rod is engaged with one of the fixing holes.

[0016] In order to make the placement frame more stable on the workbench and prevent it from moving, as a preferred embodiment of the present invention, a positioning frame is fixedly connected to the workbench. The placement frame is slidably connected to the positioning frame. A knob is threadedly connected to the positioning frame. The knob abuts against the placement frame. A spring is fixedly connected between the connecting rod and the anti - toppling plate.

[0017] In order to make the collection of finished products more convenient and facilitate handling and sorting, as a preferred embodiment of the present invention, a collection mechanism is provided on the workbench. The collection mechanism includes two collection frames installed on the workbench. A connecting block is fixedly connected to the collection frame. Two fixing blocks are fixedly connected to the workbench. The two connecting blocks are respectively slidably connected to the two fixing blocks. A plug rod is slidably connected to the fixing block, and the plug rod is engaged with the connecting block.

[0018] In order to make the collection frame easy to quickly disassemble and install, as a preferred embodiment of the present invention, a pull rod is fixedly connected to the plug rod, and a tension spring is fixedly connected between the pull rod and the fixing block.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1) By starting the first driving member, its telescopic end drives the vacuum box to move downward. When the vacuum box moves downward until the sealing ring is in close contact with the conveyor belt of the conveying device, start the second driving member, and its telescopic end drives the fixing frame to fix the packaging bag. Then start the vacuum pump, and the gas in the vacuum box is pumped away through the connecting pipe. During this process, observe the state of the packaging bag with the help of the camera. If the gas in the bag is pumped away, it indicates that the sealing of the packaging bag is unqualified, realizing the efficient detection of the sealed packaging bag.

[0021] 2) By the rotation of the stopper in the installation mechanism to resist and limit the positioning block, the disassembly and assembly efficiency of the protective cover is improved, and further the maintenance efficiency of components such as the heating block and the printing wheel is improved, making the disassembly and assembly of the protective cover convenient, facilitating the maintenance of components such as the heating block and the printing wheel inside the sealing machine body, and improving the equipment maintenance efficiency.

[0022] 3) The anti - tipping plate in the placement mechanism can effectively prevent the product from slipping out due to the tipping of the packaging bag. At the same time, separating the packaging bags from each other for easy picking can effectively prevent the packaging bags from tipping, facilitate picking, and can adjust the position of the anti - tipping plate according to actual needs, enhancing the applicability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram of the present invention;

[0024] Figure 2 is Figure 1 an enlarged schematic diagram of the structure of part A shown in;

[0025] Figure 3 is Figure 1 an enlarged schematic diagram of the structure of part B shown in;

[0026] Figure 4 is a schematic structural diagram of the mounting plate of the present invention;

[0027] Figure 5 is Figure 4 an enlarged schematic diagram of the structure of part C shown in;

[0028] Figure 6 is a schematic structural diagram of the placement frame of the present invention;

[0029] Figure 7 is Figure 6 an enlarged schematic diagram of the structure of part D shown in;

[0030] Figure 8 is a schematic structural diagram of the vacuum box of the present invention;

[0031] Figure 9 is Figure 8 an enlarged schematic diagram of the structure of part E shown in;

[0032] Figure 10 is a schematic structural diagram of the fixing frame of the present invention;

[0033] Figure 11 is a schematic structural diagram of the guiding frame of the present invention.

[0034] In the figure: 1, workbench; 2, sealing machine body; 3, detection mechanism; 301, conveying equipment; 302, mounting plate; 303, first driving member; 304, vacuum box; 305, sealing ring; 306, vacuum pump; 307, connecting pipe; 308, second driving member; 309, fixing frame; 310, camera; 311, third driving member; 312, push plate; 313, guide rod; 4, support mechanism; 401, guide frame; 402, connecting plate; 403, support leg; 404, lead screw; 405, rotating block; 5, collection mechanism; 501, collection box; 502, connecting block; 503, fixing block; 504, inserting rod; 505, tension spring; 506, pull rod; 6, installation mechanism; 601, mounting block; 602, mounting shaft; 603, torsion spring; 604, stop block; 605, positioning block; 606, grip rod; 607, limiting groove; 608, limiting block; 7, placing mechanism; 701, placing box; 702, anti-toppling plate; 703, guide sleeve; 704, connecting rod; 705, spring; 706, fixing rod; 707, fixing hole; 708, positioning frame; 709, knob; 8, protective cover; 9, guide plate. Detailed implementation mode

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] Please refer to Figure 1-11 , the present invention provides a technical solution: a plastic packaging bag sealing device, including a workbench 1, a sealing machine body 2 is installed above the workbench 1, a detection mechanism 3 is arranged on the sealing machine body 2, a protective cover 8 is detachably connected to the sealing machine body 2, an installation mechanism 6 is arranged between the protective cover 8 and the sealing machine body 2, and a placing mechanism 7 is arranged above the workbench 1;

[0037] The detection mechanism 3 includes a conveying device 301 fixedly connected to the sealing machine body 2. A mounting plate 302 is fixedly connected to the side of the conveying device 301. A first driving member 303 is installed in the mounting plate 302. A vacuum box 304 is installed at the driving end of the first driving member 303. A sealing ring 305 is installed at the bottom of the vacuum box 304. A vacuum pump 306 is installed above the vacuum box 304. A connecting pipe 307 is installed at the suction port of the vacuum pump 306. The other end of the connecting pipe 307 is fixedly connected to the vacuum box 304. A second driving member 308 is installed inside the vacuum box 304. A fixing frame 309 is installed at the driving end of the second driving member 308. A camera 310 is installed inside the vacuum box 304. A guiding plate 9 is installed on the conveying device 301 through a mounting assembly.

[0038] During specific use, the sealed packaging bag is guided by the guiding plate 9, moves onto the conveying device 301, and stays at the bottom of the vacuum box 304. At this time, start the first driving member 303 (the first driving member 303 is preferably a hydraulic rod), and its telescopic end drives the vacuum box 304 to move downward. The guiding shaft on the vacuum box 304 is slidably matched with the mounting plate 302 to ensure smooth movement. When the vacuum box 304 moves downward until the sealing ring 305 tightly abuts against the conveyor belt of the conveying device 301, start the second driving member 308 (the second driving member 308 is preferably a hydraulic rod), and its telescopic end drives the fixing frame 309 to fix the packaging bag. Then start the vacuum pump 306 to evacuate the gas inside the vacuum box 304 through the connecting pipe 307. During this process, observe the state of the packaging bag with the help of the camera 310. If the gas inside the bag is evacuated, it indicates that the sealing of the packaging bag is unqualified. At this time, the vacuum box 304 rises, and the camera 310 transmits the detection data to the controller.

[0039] A third driving member 311 is installed at the bottom of the mounting plate 302. A push plate 312 is installed at the driving end of the third driving member 311. A guiding rod 313 is installed on the push plate 312. The guiding rod 313 is slidably connected to the mounting plate 302.

[0040] During specific use, control the third driving member 311 (the third driving member 311 is preferably a hydraulic rod) through the controller, and its telescopic end drives the push plate 312 to move. The guiding rod 313 on the push plate 312 is slidably matched with the mounting plate 302 to ensure smooth movement of the push plate 312 and push away the packaging bag with unqualified sealing.

[0041] The conveying device 301 is supported by a support mechanism 4. The support mechanism 4 includes a guiding frame 401 fixedly connected to the bottom of the conveying device 301. A connecting plate 402 is slidably connected in the guiding frame 401. Support legs 403 are fixedly connected to both sides of the connecting plate 402. A lead screw 404 is rotatably connected in the guiding frame 401. The connecting plate 402 is threadedly connected to the lead screw 404. A rotating block 405 is fixedly connected to the bottom end of the lead screw 404.

[0042] During specific use, the lead screw 404 is rotated by the rotating block 405, and its thread drives the connecting plate 402 to slide within the guiding frame 401. The guiding frame 401 ensures the smoothness of the sliding of the connecting plate 402. At the same time, the connecting plate 402 drives the supporting leg 403 to contact the workbench 1, providing a stable support for the conveying device 301 and enhancing its stability.

[0043] The installation mechanism 6 includes an installation block 601 fixedly connected to the sealing machine body 2. A mounting shaft 602 is rotatably connected to the mounting block 601. A stopper 604 is fixedly connected to the mounting shaft 602. A torsion spring 603 is fixedly connected between the mounting shaft 602 and the mounting block 601. A positioning block 605 is fixedly connected above the protective cover 8. The positioning block 605 is inserted into the mounting block 601. A grip rod 606 is slidably connected in the stopper 604. A limiting block 608 is fixedly connected to the grip rod 606. The limiting block 608 is slidably connected to the stopper 604. A limiting groove 607 is provided on the mounting block 601.

[0044] During specific use, the stopper 604 is rotated by the grip rod 606. The stopper 604 drives the mounting shaft 602 to rotate. When the mounting shaft 602 rotates, the torsion spring 603 deforms. When the grip rod 606 drives the limiting block 608 to move to a position corresponding to the limiting groove 607, the grip rod 606 is pressed, causing it to slide with the stopper 604 and driving the limiting block 608 to engage with the limiting groove 607. At this time, the stopper 604 cannot rotate under the action of the torsion spring 603, and the stopper 604 no longer blocks the positioning block 605, so that the protective cover 8 can be smoothly disassembled. By using the stopper 604 to rotate to resist and limit the positioning block 605, the disassembly and assembly efficiency of the protective cover 8 is improved, and thus the maintenance efficiency of components such as the heating block and the printing wheel is increased.

[0045] The placement mechanism 7 includes a placement frame 701 installed above the workbench 1. A plurality of anti - tipping plates 702 are slidably connected within the placement frame 701. Two guide sleeves 703 are fixedly connected to the anti - tipping plates 702. A connecting rod 704 is slidably connected within the guide sleeves 703. Two fixing rods 706 are fixedly connected to the placement frame 701. A plurality of fixing holes 707 are provided on the fixing rods 706. The connecting rod 704 is engaged with one of the fixing holes 707. A positioning frame 708 is fixedly connected to the workbench 1. The placement frame 701 is slidably connected to the positioning frame 708. A knob 709 is threadedly connected to the positioning frame 708. The knob 709 abuts against the placement frame 701. A spring 705 is fixedly connected between the connecting rod 704 and the anti - tipping plate 702.

[0046] During specific use, by sequentially placing the product-containing packaging bags into the placement frame 701, the anti-tipping plate 702 can effectively prevent the packaging bags from tipping over and causing the products to slide out. At the same time, the packaging bags are spaced apart from each other, facilitating taking. Subsequently, place the placement frame 701 into the positioning frame 708 on the workbench 1. By rotating the knob 709, it is threadedly engaged with the positioning frame 708 and presses against the placement frame 701, thereby enhancing the stability between the placement frame 701 and the workbench 1. If it is necessary to adjust the position of the anti-tipping plate 702, just press the connecting rod 704. At this time, the two connecting rods 704 will slide on the guide sleeve 703, and the two connecting rods 704 slide towards each other. The setting of the guide sleeve 703 ensures a smooth sliding process. At the same time, the connecting rod 704 will compress the spring 705. When the connecting rod 704 disengages from the fixing hole 707 on the fixing rod 706, the anti-tipping plate 702 can be disassembled or adjusted. After the adjustment is completed, release the connecting rod 704. Under the action of the spring 705, the connecting rod 704 is re-engaged with the fixing rod 706 to achieve stable fixation of the anti-tipping plate 702.

[0047] A collection mechanism 5 is provided on the workbench 1. The collection mechanism 5 includes two collection frames 501 installed on the workbench 1. A connection block 502 is fixedly connected to the collection frame 501. Two fixing blocks 503 are fixedly connected to the workbench 1. The two connection blocks 502 are respectively slidably connected to the two fixing blocks 503. A plug rod 504 is slidably connected to the fixing block 503. The plug rod 504 is engaged with the connection block 502. A pull rod 506 is fixedly connected to the plug rod 504. A tension spring 505 is fixedly connected between the pull rod 506 and the fixing block 503.

[0048] During specific use, when disassembling the collection frame 501, pull the pull rod 506 upward. The tension spring 505 elongates accordingly, and at the same time drives the plug rod 504 to move upward. When the plug rod 504 disengages from the connection block 502, the collection frame 501 together with the connection block 502 can be slid out from the fixing block 503, facilitating the removal of the products in the collection frame 501. Through the engagement of the fixing block 503 and the connection block 502, the collection frame 501 is effectively prevented from shifting under the gravity of the falling products, and the setting of the collection frame 501 facilitates the centralized collection of the processed products.

[0049] Working principle: Sequentially place the product-containing packaging bags into the placement frame 701. Subsequently, place the placement frame 701 into the positioning frame 708 on the workbench 1. By rotating the knob 709, it is threadedly engaged with the positioning frame 708 and presses against the placement frame 701;

[0050] Next, place the packaging bag on the sealing machine body 2. The sealing machine body 2 drives the conveyor belt to run through the motor and the transmission assembly, so that the packaging items to be sealed continuously pass through the heating device. The heating device is generally composed of heating wires or heating blocks. When the packaging material passes through the heating area, the plastic film at the sealing part quickly softens and melts. Under the extrusion of the pressing wheel, the softened materials are bonded together and form a firm sealed joint after cooling. The sealed packaging bag is guided by the guide plate 9, moves onto the conveying device 301, and stays at the bottom of the vacuum chamber 304. When the vacuum chamber 304 moves downward until the sealing ring 305 tightly contacts the conveyor belt of the conveying device 301, start the second driving member 308 (the second driving member 308 is preferably a hydraulic rod). Its telescopic end drives the fixing frame 309 to fix the packaging bag. Then start the vacuum pump 306 to evacuate the gas in the vacuum chamber 304 through the connecting pipe 307. During this process, observe the state of the packaging bag with the help of the camera 310;

[0051] When disassembling the collection frame 501, pull the pull rod 506 upward. The tension spring 505 elongates accordingly and at the same time drives the insertion rod 504 to move upward. When the insertion rod 504 disengages from the connection block 502, the collection frame 501 together with the connection block 502 can be slid out from the fixed block 503.

[0052] The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A plastic packaging bag sealing device, comprising a workbench (1), characterized in that: A sealing machine body (2) is installed above the workbench (1), a detection mechanism (3) is provided on the sealing machine body (2), a protective cover (8) is detachably connected to the sealing machine body (2), a mounting mechanism (6) is provided between the protective cover (8) and the sealing machine body (2), and a placement mechanism (7) is provided above the workbench (1); The detection mechanism (3) comprises a conveying device (301) fixedly connected to the sealing machine body (2), a mounting plate (302) fixedly connected to the side of the conveying device (301), a first driving member (303) mounted in the mounting plate (302), a vacuum box (304) mounted on the driving end of the first driving member (303), a sealing ring (305) mounted on the bottom of the vacuum box (304), and a vacuum pump (306) mounted above the vacuum box (304). 6), a connecting pipe (307) is installed at the suction port of the vacuum pump (306), the other end of the connecting pipe (307) is fixedly connected to the vacuum box (304), a second driving member (308) is installed inside the vacuum box (304), a fixing frame (309) is installed at the driving end of the second driving member (308), a camera (310) is installed inside the vacuum box (304), and a guide plate (9) is installed on the conveying device (301) through a mounting assembly.

2. The plastic packaging bag sealing device according to claim 1, wherein: A third driving member (311) is installed at the bottom of the mounting plate (302), a push plate (312) is installed at the driving end of the third driving member (311), a guide rod (313) is installed on the push plate (312), and the guide rod (313) is slidably connected to the mounting plate (302).

3. The plastic packaging bag sealing device according to claim 2, characterized in that: The conveying device (301) is supported by a support mechanism (4), wherein the support mechanism (4) comprises a guide frame (401) fixedly connected to the bottom of the conveying device (301), a connecting plate (402) is slidably connected to the guide frame (401), and support legs (403) are fixedly connected to both sides of the connecting plate (402).

4. A plastic packaging bag sealing device according to claim 3, characterized in that: A screw rod (404) is rotatably connected in the guide frame (401), the connecting plate (402) is threadedly connected to the screw rod (404), and a rotating block (405) is fixedly connected to the bottom end of the screw rod (404).

5. A plastic packaging bag sealing device according to claim 1, characterized in that: The mounting mechanism (6) comprises a mounting block (601) fixedly connected to the sealing machine body (2); a mounting shaft (602) is rotatably connected to the mounting block (601); a stopper (604) is fixedly connected to the mounting shaft (602); a torsion spring (603) is fixedly connected between the mounting shaft (602) and the mounting block (601); a positioning block (605) is fixedly connected above the protective cover (8); and the positioning block (605) is plugged into the mounting block (601).

6. The plastic packaging bag sealing device according to claim 5, characterized in that: The stopper (604) is slidably connected to a gripping rod (606), a limiting block (608) is fixedly connected to the gripping rod (606), the limiting block (608) is slidably connected to the stopper (604), and a limiting groove (607) is provided on the mounting block (601).

7. A plastic packaging bag sealing device according to claim 1, characterized in that: The placement mechanism (7) includes a placement frame (701) installed above the workbench (1). A plurality of anti - toppling plates (702) are slidably connected in the placement frame (701). Two guide sleeves (703) are fixedly connected to the anti - toppling plate (702). A connecting rod (704) is slidably connected in the guide sleeve (703). Two fixed rods (706) are fixedly connected to the placement frame (701). A plurality of fixing holes (707) are provided on the fixed rod (706), and the connecting rod (704) is engaged with one of the fixing holes (707).

8. The plastic packaging bag sealing device according to claim 7, characterized in that: A positioning frame (708) is fixedly connected to the workbench (1). The placement frame (701) is slidably connected to the positioning frame (708). A knob (709) is threadedly connected to the positioning frame (708). The knob (709) abuts against the placement frame (701). A spring (705) is fixedly connected between the connecting rod (704) and the anti - toppling plate (702).

9. The plastic packaging bag sealing device according to claim 1, characterized in that: A collection mechanism (5) is arranged on the workbench (1). The collection mechanism (5) includes two collection frames (501) installed on the workbench (1). A connecting block (502) is fixedly connected to the collection frame (501). Two fixed blocks (503) are fixedly connected to the workbench (1). The two connecting blocks (502) are respectively slidably connected to the two fixed blocks (503). A plug rod (504) is slidably connected to the fixed block (503), and the plug rod (504) is engaged with the connecting block (502).

10. The plastic packaging bag sealing device according to claim 9, characterized in that: A pull rod (506) is fixedly connected to the plug rod (504). A tension spring (505) is fixedly connected between the pull rod (506) and the fixed block (503).

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