Automobile sealing strip with U-shaped framework structure

Abstract

The invention relates to the technical field of automobile sealing strips, and discloses an automobile sealing strip with a U-shaped framework structure, which comprises a rubber sealing layer, a U-shaped supporting framework is fixedly connected in the rubber sealing layer, a connecting layer is fixedly connected to the top end of the rubber sealing layer, and a buffer foam pipe is fixedly connected to the top end of the connecting layer. A side exhaust hole is formed in the top end of the buffer bubble pipe, an exhaust mechanism is fixedly connected to the interior of the side exhaust hole, upper clamping teeth are fixedly connected to the middle of the interior of the rubber sealing layer, and a bonding mechanism is fixedly connected to the top ends of the upper clamping teeth; the rubber sealing layer is clamped on the edge of the automobile sheet metal part, and after the rubber sealing layer and the edge of the sheet metal part are in a semi-connection state, the rubber sealing layer is pressed again, so that the rubber sealing layer is completely attached to the edge of the sheet metal part, and the upper clamping teeth face upwards and are completely attached to the edge of the sheet metal part; and the glue solution in the glue solution film bag is extruded from the bag opening to a position between the rubber sealing layer and the sheet metal part, so that the glue solution is prevented from drying up when the glue solution is not bonded.

Description

Technical Field

[0001] The present invention relates to the technical field of automotive sealing strips, and more particularly to an automotive sealing strip having a U-shaped skeleton structure. Background Art

[0002] As a key component of the vehicle body sealing system, automotive sealing strips undertake multiple functions such as sound insulation and noise reduction, waterproofing and dustproofing, buffering and shock absorption, and aerodynamic optimization in the automotive industry. Traditional sealing strips mostly use single rubber materials or simple composite structures, and their mechanical strength, durability, and assembly accuracy are difficult to meet the requirements of modern automotive lightweight, long-life, and fine manufacturing. Especially for dynamic sealing areas such as doors, windows, and skylights, not only does the material need to have excellent elastic recovery ability, but also the overall structure should still maintain a stable sealing effect after long-term compression deformation; In response to this situation, a sealing strip structure using a thermoplastic elastomer metal-plastic composite skeleton has gradually become popular. The skeleton in this sealing strip structure is usually manufactured with a U-shaped cross-section from galvanized steel, aluminum alloy, or engineering plastics, and is compounded with rubber through a coextrusion process to form a composite structure. After forming the composite mechanism, it can effectively wrap the edge of the vehicle body sheet metal and provide a stable support base point; When the current automotive sealing strips are in use, the sealing strips need to be clamped and fixed on the sheet metal edges such as automotive doors or windows. To ensure sufficient firmness between the two, glue is generally applied inside the sealing strips or on the sheet metal edges, and the firmness between the two is increased by means of adhesion. However, when the glue is applied inside the sealing strips or on the sheet metal edges, when it comes to installation, the glue is easily solidified and dried up in the air, and cannot achieve the adhesive connection effect. Moreover, when the skeleton inside the current sealing strips is connected to the external rubber sealing layer, the situation where the skeleton is separated from the rubber sealing layer easily occurs; When the automotive sealing strip is in use, the sealing strip discharges gas through the gas holes on both sides of the bubble tube. At this time, the bubble tube is compressed and elastically deformed, thereby playing a buffering effect. The gas discharges from both sides at a relatively slow speed, and the deformation may not be timely, resulting in a poor buffering effect. Moreover, if a large amount of dust enters the sealing body, it will also have an adverse impact on the buffering performance of the sealing strip, and the bubble tube is prone to the situation of being unable to reset after multiple deformations. Summary of the Invention

[0003] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides an automotive sealing strip having a U-shaped skeleton structure to solve the technical problems raised in the background art.

[0004] To achieve the above object, the present invention provides the following technical solution: An automobile sealing strip with a U-shaped skeleton structure, including a rubber sealing layer, a U-shaped support skeleton is fixedly connected inside the rubber sealing layer, a connecting layer is fixedly connected to the top of the rubber sealing layer, a buffer bubble tube is fixedly connected to the top of the connecting layer, side exhaust holes are opened at the top of the buffer bubble tube, an exhaust mechanism is fixedly connected inside the side exhaust holes, a support mechanism is fixedly connected inside the buffer bubble tube, air exchange holes are opened on both sides of the buffer bubble tube, lower clamping teeth are fixedly connected to the bottom end inside the rubber sealing layer, upper clamping teeth are fixedly connected to the middle inside the rubber sealing layer, and a bonding mechanism is fixedly connected to the top of the upper clamping teeth; The bonding mechanism includes a glue liquid film bag filled with glue liquid, a bag mouth is fixedly connected to the top of the glue liquid film bag, a bonding layer is adhesively bonded inside the bag mouth, and the bottom end of the glue liquid film bag is fixedly connected to the top of the upper clamping teeth.

[0005] In a preferred embodiment, dust-proof sponges are fixedly connected inside the air exchange holes, the support mechanism and the exhaust mechanism are alternately distributed inside the buffer bubble tube, the U-shaped support skeletons are equidistantly distributed inside the rubber sealing layer, and concave-convex textures are provided on both the inner and outer surfaces of the U-shaped support skeletons.

[0006] In a preferred embodiment, the support mechanism includes fixed marbles fixedly connected to the inside of the buffer bubble tube, elastic rods are fixedly connected to the sides of the fixed marbles, four fixed marbles and elastic rods are combined into a group, and the fixed marbles and elastic rods in a group are alternately arranged.

[0007] In a preferred embodiment, a group of fixed marbles and elastic rods are combined into a regular quadrilateral, the angle between adjacent two elastic rods is a right angle, and a group of fixed marbles and elastic rods are fixedly connected to the buffer bubble tube in a rhombus shape inside the buffer bubble tube.

[0008] In a preferred embodiment, the exhaust mechanism includes a fixed cylinder located inside the side exhaust hole and fixedly connected to the side exhaust hole, a second support assembly is fixedly connected to the top end inside the fixed cylinder, and a sealing sponge is fixedly connected to the bottom end inside the fixed cylinder.

[0009] In a preferred embodiment, a first support assembly is movably connected to the top of the sealing sponge, the side of the first support assembly is fixedly connected to the inside of the fixed cylinder, an exhaust valve flap is movably connected to the top of the first support assembly, and the side of the exhaust valve flap is fixedly connected to the inside of the fixed cylinder.

[0010] In a preferred embodiment, the number of the exhaust valves is four, the four exhaust valves have the same shape, and the distance between the second support assembly and the exhaust valves is half of the diameter of each exhaust valve. The second support assembly has the same structure as the first support assembly.

[0011] In a preferred embodiment, the second support assembly includes an outer limiting cylinder fixedly connected to the inner side of the fixed cylinder. A first connecting plate is fixedly connected to the inner side of the outer limiting cylinder. A middle limiting cylinder is fixedly connected to the inner side of the first connecting plate. A second connecting cylinder is fixedly connected to the inner side of the middle limiting cylinder. An inner limiting cylinder is fixedly connected to the inner side of the second connecting cylinder.

[0012] The technical effects and advantages of the present invention: 1. In the present invention, the rubber sealing layer is clamped on the edge of the automotive sheet metal part. After the lower clamping teeth contact the edge of the sheet metal part, when the whole rubber sealing layer is in a semi-connected state with the edge of the sheet metal part, the rubber sealing layer is pressed again, so that the rubber sealing layer is completely attached to the edge of the sheet metal part. At this time, the upper clamping teeth rotate upward and fit with the edge of the sheet metal part. After the upper clamping teeth rotate, the glue in the glue film bag is extruded from the bag mouth. At this time, the bonding layer is separated from the bag mouth, and the glue is extruded from the bag mouth between the rubber sealing layer and the sheet metal part, avoiding the glue from drying up before bonding. 2. When buffering in the present invention, the buffer bubble tube will deform. When the upper end and the side of the buffer bubble tube are squeezed and deformed, the elastic rod will be stretched vertically or laterally. After the extrusion is received, the stretched elastic rod will reset, thereby driving the buffer bubble tube to reset, so that the buffer bubble tube can quickly reset, ensuring that the buffer bubble tube can still quickly reset after multiple deformations. The surface of the U-shaped support skeleton is provided with concave and convex textures, which are better connected with the rubber sealing layer and are not easy to fall off from each other. 3. When the buffer bubble tube of the present invention is squeezed and deformed for buffering, the gas in the buffer bubble tube can be discharged from both the air exchange hole and the side exhaust hole, realizing the rapid discharge of the gas and ensuring the buffering effect. When the gas is discharged from the inside of the exhaust mechanism through the side exhaust hole, the exhaust valve bends upward when the gas is discharged, and the gas is discharged from the junction of the four exhaust valves. After the discharge, the upward-bent exhaust valve resets, and the lower part of the exhaust valve is supported by the first support assembly for sealing to prevent dust from entering. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of the overall structure of the present invention.

[0014] Figure 2 is a schematic diagram of the overall internal structure of the present invention.

[0015] Figure 3 is a schematic diagram of the internal structure of the rubber sealing layer of the present invention.

[0016] Figure 4 This is a schematic structural diagram of the U-shaped support skeleton of the present invention.

[0017] Figure 5 This is a schematic overall structural diagram of the bonding mechanism of the present invention.

[0018] Figure 6 This is a schematic sectional structural diagram of the bonding mechanism of the present invention.

[0019] Figure 7 This is a schematic structural diagram of the support mechanism of the present invention.

[0020] Figure 8 This is a schematic overall structural diagram of the exhaust mechanism of the present invention.

[0021] Figure 9 This is a schematic exploded structural diagram of the exhaust mechanism of the present invention.

[0022] Figure 10 This is a schematic structural diagram of the first support assembly and the second support group of the present invention.

[0023] Reference numerals are: 1, rubber sealing layer; 2, U-shaped support skeleton; 3, connecting layer; 4, buffer bubble tube; 5, side exhaust hole; 6, exhaust mechanism; 601, fixed cylinder; 602, sealing sponge; 603, first support assembly; 604, exhaust valve; 605, second support assembly; 6051, outer limiting cylinder; 6052, first connecting plate; 6053, middle limiting cylinder; 6054, second connecting cylinder; 6055, inner limiting cylinder; 7, support mechanism; 701, fixed ball; 702, elastic rod; 8, upper engaging tooth; 9, bonding mechanism; 901, glue film bag; 902, bag mouth; 903, bonding layer; 10, lower engaging tooth; 11, air exchange hole; 12, dust-proof sponge. Detailed implementation manners

[0024] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the drawings in the present invention. Additionally, the forms of each structure described in the following implementation manners are merely examples. An automotive sealing strip having a U-shaped skeleton structure involved in the present invention is not limited to the structures described in the following implementation manners. All other implementation manners obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0025] Refer to Figures 1 - 4, the present invention provides an automotive sealing strip with a U-shaped skeleton structure, including a rubber sealing layer 1, a U-shaped support skeleton 2 fixedly connected inside the rubber sealing layer 1, a connection layer 3 fixedly connected to the top of the rubber sealing layer 1, a buffer bubble tube 4 fixedly connected to the top of the connection layer 3, side exhaust holes 5 opened at the top of the buffer bubble tube 4, an exhaust mechanism 6 fixedly connected inside the side exhaust holes 5, a support mechanism 7 fixedly connected inside the buffer bubble tube 4, air exchange holes 11 opened on both sides of the buffer bubble tube 4, lower teeth 10 fixedly connected to the bottom end inside the rubber sealing layer 1, upper teeth 8 fixedly connected to the middle inside the rubber sealing layer 1, a bonding mechanism 9 fixedly connected to the top of the upper teeth 8, dust-proof sponges 12 fixedly connected inside the air exchange holes 11, the support mechanism 7 and the exhaust mechanism 6 are alternately distributed inside the buffer bubble tube 4, the U-shaped support skeletons 2 are equidistantly distributed inside the rubber sealing layer 1, and concave-convex textures are provided on both the inner and outer surfaces of the U-shaped support skeletons 2.

[0026] In the embodiment of the present application, dust-proof sponges 12 are fixedly connected inside the air exchange holes 11 on both sides of the buffer bubble tube 4. Therefore, when the buffer bubble tube 4 deforms and inhales, dust can be intercepted. The support mechanism 7 and the exhaust mechanism 6 are alternately distributed inside the buffer bubble tube 4, and their distribution is more uniform, which can achieve better exhaust and rebound support effects. Concave-convex textures are provided on both the inner and outer surfaces of the U-shaped support skeleton 2. By connecting with the rubber sealing layer 1 through the concave-convex textures, the connection between the rubber sealing layer 1 and the U-shaped support skeleton 2 is tighter and not easily separated.

[0027] Refer to Figure 5 And Figure 6 , the bonding mechanism 9 includes a glue film bag 901 filled with glue, a bag mouth 902 fixedly connected to the top of the glue film bag 901, a bonding layer 903 adhesively bonded inside the bag mouth 902, and the bottom end of the glue film bag 901 is fixedly connected to the top of the upper teeth 8.

[0028] In the embodiment of the present application, when the upper teeth 8 are twisted upward, the glue inside the glue film bag 901 will be squeezed upward. When the glue inside the glue film bag 901 is squeezed to the position where the bag mouth 902 is located, the bag mouth 902 and the bonding layer 903 are separated, and the adhesively bonded part between the bag mouth 902 and the bonding layer 903 is separated. The glue will be squeezed out from above the bag mouth 902 and then flow into the space between the rubber sealing layer 1 and the edge of the sheet metal part to bond between the edge of the sheet metal part and the rubber sealing layer 1, avoiding the drying up of the glue during pre-coating and avoiding the operation error of sticking to a non-preset position when using double-sided adhesive for bonding.

[0029] Refer to Figure 7, the support mechanism 7 includes a fixed ball 701 fixedly connected to the inside of the buffer bubble tube 4. A resilient rod 702 is fixedly connected to the side of the fixed ball 701. Four fixed balls 701 and the resilient rod 702 are combined into a group, and the fixed balls 701 and the resilient rod 702 within a group are arranged alternately. A group of fixed balls 701 and the resilient rod 702 form a regular quadrilateral, and the angle between two adjacent resilient rods 702 is a right angle. Moreover, a group of fixed balls 701 and the resilient rod 702 are fixedly connected to the buffer bubble tube 4 in a rhombus shape inside the buffer bubble tube 4.

[0030] In the embodiment of the present application, when the buffer bubble tube 4 is deformed and squeezed, when subjected to squeezing forces in the vertical and horizontal directions, the angle between two adjacent resilient rods 702 will become larger or smaller, and the resilient rod 702 will be squeezed and deformed. When the buffer bubble tube 4 is not subjected to a squeezing force, the deformed resilient rod 702 will reset, enabling the buffer bubble tube 4 to recover faster and allowing multiple squeezes. When the buffer bubble tube 4 is not deformed, the resilient rod 702 can support the buffer bubble tube 4 to prevent the buffer bubble tube 4 from failing to recover in time and being unable to achieve a buffering effect.

[0031] Referring to Figure 8 , Figure 9 and Figure 10 , the exhaust mechanism 6 includes a fixed cylinder 601 located in the side exhaust hole 5 and fixedly connected to the side exhaust hole 5. A second support assembly 605 is fixedly connected to the top end inside the fixed cylinder 601. A sealing sponge 602 is fixedly connected to the bottom end inside the fixed cylinder 601. A first support assembly 603 is movably connected to the top end of the sealing sponge 602. The side of the first support assembly 603 is fixedly connected to the inside of the fixed cylinder 601. An exhaust valve flap 604 is movably connected to the top end of the first support assembly 603. The side of the exhaust valve flap 604 is fixedly connected to the inside of the fixed cylinder 601. The number of exhaust valve flaps 604 is four, and the four exhaust valve flaps 604 have the same shape. Moreover, the distance between the second support assembly 605 and the exhaust valve flap 604 is half of the diameter of each exhaust valve flap 604. The second support assembly 605 has the same structure as the first support assembly 603. The second support assembly 605 includes an outer limit cylinder 6051 fixedly connected to the inside of the fixed cylinder 601. A first connecting plate 6052 is fixedly connected to the inside of the outer limit cylinder 6051. A middle limit cylinder 6053 is fixedly connected to the inside of the first connecting plate 6052. A second connecting cylinder 6054 is fixedly connected to the inside of the middle limit cylinder 6053. An inner limit cylinder 6055 is fixedly connected to the inside of the second connecting cylinder 6054.

[0032] In the embodiment of the present application, when the gas is discharged through the exhaust mechanism 6, the gas will pass through the exhaust valve 604. When discharging from the exhaust valve 604, the gas will squeeze the exhaust valve 604 upward, causing the exhaust valve 604 to bend upward. The gas is discharged upward through the junction of the four exhaust valves 604. After the gas is discharged, the exhaust valve 604 will reset and close. When the exhaust valve 604 is closed, a first support component 603 is provided below the exhaust valve 604 to prevent the exhaust valve 604 from bending downward, prevent dust from entering from the location of the exhaust valve 604, and prevent dust from entering the buffer bubble tube 4. There is a space between the exhaust valve 604 and the second support component 605, enabling the exhaust valve 604 to bend upward and ensuring the exhaust effect of the exhaust valve 604. At the bottom of the fixed cylinder 601, a sealing sponge 602 is provided to prevent a small amount of dust after long-term use from directly entering the buffer bubble tube 4. The second support component 605 can protect the exhaust valve 604 and prevent the exhaust valve 604 from being damaged and unable to achieve the interception effect. Inside the second support component 605, the outer limit cylinder 6051, the first connecting plate 6052, the middle limit cylinder 6053, the second connecting cylinder 6054, and the inner limit cylinder 6055 are arranged alternately. Therefore, while providing support, the gas can pass freely, ensuring the exhaust effect.

[0033] Working principle of the present invention: During installation, the rubber sealing layer 1 is connected to the edge of the sheet metal part. First, half of it is connected. At this time, half of the internal connection between the sheet metal part and the rubber sealing layer 1 is completed. Therefore, only the lower teeth 10 are squeezed and deformed. After connecting half of the entire rubber sealing layer 1 to the entire edge of the sheet metal part, continue to press the rubber sealing layer 1 so that the rubber sealing layer 1 bends and fits with the edge of the sheet metal part. When the rubber sealing layer 1 bends and fits with the edge of the sheet metal part, the upper teeth 8 twist upward and squeeze the glue in the glue film bag 901 upward. When the glue in the glue film bag 901 is squeezed to the location of the bag mouth 902, the bag mouth 902 is separated from the bonding layer 903, and the glue will be extruded from above the bag mouth 902 and then flow into the rubber sealing layer 1 and the edge of the sheet metal part to bond between the edge of the sheet metal part and the rubber sealing layer 1. After the rubber sealing layer 1 is bonded to the edge of the sheet metal part, buffering is carried out by squeezing the buffer bubble tube 4. When the buffer bubble tube 4 is squeezed, when the squeezing direction is vertical or horizontal, the buffer bubble tube 4 will deform in the corresponding direction. When the buffer bubble tube 4 deforms, the fixed ball 701 and the elastic rod 702 will be stretched horizontally or vertically. Therefore, when the squeezing force applied to the buffer bubble tube 4 disappears, the fixed ball 701 and the elastic rod 702 will automatically reset, enabling the buffer bubble tube 4 to recover relatively quickly after being squeezed multiple times. When the buffer bubble tube 4 is squeezed and deformed, the gas in the buffer bubble tube 4 will be discharged through the air exchange holes 11 on both sides of the buffer bubble tube 4 and the side exhaust holes 5 above. When discharged through the side exhaust holes 5, the gas will pass through the sealing sponge 602 and the first support assembly 603 and then be discharged from the exhaust valve 604. When discharged from the exhaust valve 604, the gas will upwardly squeeze the exhaust valve 604, causing the exhaust valve 604 to bend upward. The gas is discharged upward through the junction of the four exhaust valves 604. After the gas is discharged, the exhaust valve 604 will reset and close. When the buffer bubble tube 4 is reset after being squeezed, when the gas enters through the air exchange holes 11, it will intercept dust through the dust-proof sponge 12. And when the exhaust valve 604 is closed, there is a first support assembly 603 below the exhaust valve 604 to prevent the exhaust valve 604 from bending downward, prevent dust from entering from the location of the exhaust valve 604, and prevent dust from entering the buffer bubble tube 4.

[0034] Finally: The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An automotive sealing strip with a U-shaped skeleton structure, comprising a rubber sealing layer (1), characterized in that: Inside the rubber sealing layer (1), a U-shaped support skeleton (2) is fixedly connected. At the top of the rubber sealing layer (1), a connection layer (3) is fixedly connected. At the top of the connection layer (3), a buffer bubble tube (4) is fixedly connected. At the top of the buffer bubble tube (4), a side exhaust hole (5) is provided. Inside the side exhaust hole (5), an exhaust mechanism (6) is fixedly connected. Inside the buffer bubble tube (4), a support mechanism (7) is fixedly connected. On both sides of the buffer bubble tube (4), air exchange holes (11) are provided. At the bottom end inside the rubber sealing layer (1), a lower clamping tooth (10) is fixedly connected. In the middle inside the rubber sealing layer (1), an upper clamping tooth (8) is fixedly connected. At the top of the upper clamping tooth (8), an adhesive mechanism (9) is fixedly connected; the adhesive mechanism (9) includes a glue film bag (901) filled with glue. At the top of the glue film bag (901), a bag mouth (902) is fixedly connected. Inside the bag mouth (902), an adhesive layer (903) is adhesively connected. The bottom end of the glue film bag (901) is fixedly connected to the top of the upper clamping tooth (8).

2. The automotive sealing strip with a U-shaped skeleton structure according to claim 1, characterized in that: Inside each of the air exchange holes (11), a dust-proof sponge (12) is fixedly connected. The support mechanism (7) and the exhaust mechanism (6) are alternately distributed inside the buffer bubble tube (4). The U-shaped support skeletons (2) are evenly distributed inside the rubber sealing layer (1), and concave and convex textures are provided on both the inner and outer surfaces of the U-shaped support skeletons (2).

3. The automotive sealing strip with a U-shaped skeleton structure according to claim 1, wherein: The support mechanism (7) includes fixed marbles (701) fixedly connected to the inside of the buffer bubble tube (4). On the side of each fixed marble (701), an elastic rod (702) is fixedly connected. Four fixed marbles (701) and the elastic rod (702) are combined into a group, and the fixed marbles (701) and the elastic rod (702) in a group are alternately arranged.

4. The automotive sealing strip with a U-shaped skeleton structure according to claim 3, characterized in that: A group of fixed marbles (701) and the elastic rod (702) are combined into a regular quadrilateral. The angle between two adjacent elastic rods (702) is a right angle, and a group of fixed marbles (701) and the elastic rod (702) are fixedly connected to the buffer bubble tube (4) in a rhombus shape inside the buffer bubble tube (4).

5. The automotive sealing strip with a U-shaped skeleton structure according to claim 1, characterized in that: The exhaust mechanism (6) includes a fixed cylinder (601) located inside the side exhaust hole (5) and fixedly connected to the side exhaust hole (5). At the top end inside the fixed cylinder (601), a second support assembly (605) is fixedly connected. At the bottom end inside the fixed cylinder (601), a sealing sponge (602) is fixedly connected.

6. The automotive sealing strip with a U-shaped skeleton structure according to claim 5, characterized in that: At the top of the sealing sponge (602), a first support assembly (603) is movably connected. The side of the first support assembly (603) is fixedly connected to the inside of the fixed cylinder (601). At the top of the first support assembly (603), an exhaust valve flap (604) is movably connected. The side of the exhaust valve flap (604) is fixedly connected to the inside of the fixed cylinder (601).

7. The automotive sealing strip with a U-shaped skeleton structure according to claim 6, characterized in that: The number of the exhaust valves (604) is four. The four exhaust valves (604) have the same shape, and the distance between the second support assembly (605) and the exhaust valves (604) is half of the diameter of each exhaust valve (604). The second support assembly (605) has the same structure as the first support assembly (603).

8. The automotive sealing strip with a U-shaped skeleton structure according to claim 7, characterized in that: The second support assembly (605) includes an outer limit cylinder (6051) fixedly connected to the inner side of the fixed cylinder (601). A first connecting plate (6052) is fixedly connected to the inner side of the outer limit cylinder (6051). A middle limit cylinder (6053) is fixedly connected to the inner side of the first connecting plate (6052). A second connecting cylinder (6054) is fixedly connected to the inner side of the middle limit cylinder (6053). An inner limit cylinder (6055) is fixedly connected to the inner side of the second connecting cylinder (6054).

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