A sealing structure for polymerization kettle

Abstract

The present application relates to the field of polymerization kettles and discloses a sealing structure for a polymerization kettle, comprising a seat ring integrally formed at the edge of the top opening of the kettle body, a side skirt ring integrally formed at the outer edge of the kettle cover and in a horizontal shape, and a ring barrel integrally formed at the inner edge of the kettle cover and in a vertical shape. An upper groove communicating with the top surface of the seat ring is provided on the inner wall of the seat ring, a rubber sealing ring is placed in the upper groove, an intermediate ring member is abutted against the top of the rubber sealing ring, an outer slot is provided on the outer wall of the intermediate ring member, an inner slot is provided on the inner wall of the intermediate ring member, an outer rubber ring is inserted into the outer slot, an inner rubber ring is inserted into the inner slot, a pressure ring is formed between the side skirt ring and the ring barrel, and the pressure ring is used to abut against the top surface of the intermediate ring member. The present application realizes multiple sealing, hinders the outflow of tiny chemical substances in the airflow, and reduces chemical damage to external staff.

Description

Technical Field

[0001] The present application relates to the field of polymerization kettles, and in particular to a sealing structure of a polymerization kettle. Background Art

[0002] Polymerization reactors are the primary equipment for preparing polymer compounds. They are typically vertical cylindrical autoclaves. The polymerization reactor is heated by thermal oil, resulting in high temperatures and viscosities during the polymerization process. The reactor's outer shell is typically divided into two parts: the reactor body and the lid. After extended use, the lid often needs to be removed to facilitate maintenance or cleaning.

[0003] However, in the process of implementing relevant technical solutions, it was found that at least the following technical problems exist: the gathering reaction is often an exothermic reaction, which will generate airflow. The airflow will carry tiny chemical substances of the gathering reaction. The tiny chemical substances in the airflow will flow out from the gap between the kettle cover and the kettle body, and then cause chemical damage to external workers. Summary of the Invention

[0004] The present application solves the technical problem in the prior art that tiny chemical substances in the air flow will flow out from the gap between the reactor cover and the reactor body by providing a polymerization reactor sealing structure, realizes multiple seals, hinders the outflow of tiny chemical substances in the air flow, and reduces chemical damage to external workers.

[0005] The present application provides a sealing structure of a polymerization kettle, comprising a seat ring integrally formed at the edge of the top opening of the kettle body, a side skirt ring integrally formed at the outer edge of the kettle cover and in a horizontal shape, and a ring cylinder integrally formed at the inner edge of the kettle cover and in a vertical shape. The inner wall of the seat ring is provided with an upper groove connected to the top surface of the seat ring, a rubber sealing ring is placed in the upper groove, and an intermediate ring member is abutted above the rubber sealing ring, an outer slot is provided on the outer wall of the intermediate ring member, an inner slot is provided on the inner wall of the intermediate ring member, an outer rubber ring is inserted in the outer slot, and an inner rubber ring is inserted in the inner slot, a pressure ring is formed between the side skirt ring and the ring cylinder, and the pressure ring is used to abut against the top surface of the intermediate ring member.

[0006] Furthermore, a number of equally spaced mounting holes are provided along a circumference of the side skirt, a number of equally spaced columns are vertically fixed to the top surface of the seat ring, the columns pass through the mounting holes, and locking nuts are abutted on the upper and lower surfaces of the side skirt ring, and the locking nuts are threadedly connected to the columns.

[0007] Furthermore, a lower groove is provided at the bottom of the upper groove, the lower groove is located below the upper groove, the top surface of the lower groove is connected to the upper groove, and the bottom surface of the intermediate ring is integrally formed with a lower ring, which is used to abut against the lower groove.

[0008] Furthermore, a plurality of mounting countersunk holes are provided on the bottom surface of the lower side ring, and the plurality of mounting countersunk holes are evenly distributed around the circumference of the lower side ring. A spring is provided in the mounting countersunk hole, and one end of the spring is fixed to the bottom surface of the mounting countersunk hole, and the other end is fixed to the bottom of the lower side groove. When the spring is in a non-stressed state, the intermediate ring part is separated from the rubber sealing ring.

[0009] Furthermore, a plurality of outer ring strips are formed on a side surface of the outer rubber ring away from the outer slot, and the plurality of outer ring strips are distributed at equal intervals along the height direction of the outer rubber ring, and the outer ring strips are used to abut against the groove wall of the upper groove, and a plurality of inner ring strips are formed on a side surface of the inner rubber ring away from the inner slot, and the plurality of inner ring strips are distributed at equal intervals along the height direction of the inner rubber ring, and the inner ring strips are used to abut against the outer wall of the ring cylinder.

[0010] Furthermore, a horizontal guide hole is provided on the outer peripheral surface of the pressure ring, and a vertical guide hole is provided on the lower surface of the pressure ring. The guide hole is close to the outer wall of the ring tube, and the guide hole is connected to the guide hole. The guide hole is used to introduce sealing oil.

[0011] Furthermore, a chamfered right-angled edge is provided at the edge of the top surface of the intermediate ring close to the inner rubber ring, and the top surface of the inner rubber ring is located below the bottom edge of the chamfered right-angled edge.

[0012] Furthermore, the height of the annular cylinder is longer than that of the inner rubber ring, and the bottom surface of the annular cylinder is located below the bottom surface of the inner rubber ring when the pressure ring contacts the intermediate ring.

[0013] One or more technical solutions provided in this application have at least the following technical effects or advantages:

[0014] Due to the use of an intermediate ring, a rubber sealing ring, an outer rubber ring and an inner rubber ring, the rubber sealing ring will fill the gap between the intermediate ring and the upper groove under the extrusion deformation of the intermediate ring, thereby playing a sealing role. After the intermediate ring enters the upper groove, the inner rubber ring and the outer rubber ring seal part of the position between the kettle cover and the kettle body. In addition, the use of sealing oil can further improve the sealing effect of the inner rubber ring and the outer rubber ring, realize multiple seals, hinder the outflow of tiny chemical substances in the airflow, and reduce chemical damage to external staff. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic structural diagram of a polymerization kettle cover in an embodiment of the present application being arranged on the kettle body;

[0016] Figure 2 This is a schematic diagram of a partial explosion structure of the sealing structure in the polymerization kettle of the embodiment of the present application;

[0017] Figure 3 This is a schematic diagram of the kettle cover structure of an embodiment of the present application;

[0018] Figure 4 This is a schematic diagram of the kettle structure of an embodiment of the present application;

[0019] Figure 5 This is a cross-sectional schematic diagram of the sealing structure between the kettle body and the kettle cover in an embodiment of the present application.

[0020] In the figure: 101, kettle body; 102, kettle cover; 103, column; 104, locking nut; 11, seat ring; 111, upper groove; 112, lower groove; 12, side skirt ring; 121, mounting hole; 13, ring cylinder; 14, rubber sealing ring; 15, intermediate ring; 1501, chamfered right-angle edge; 151, outer slot; 152, inner slot; 153, lower ring; 1531, mounting countersunk hole; 16, outer rubber ring; 161, outer ring strip; 17, inner rubber ring; 171, inner ring strip; 18, pressure ring; 181, diversion horizontal hole; 182, diversion vertical hole; 19, spring. DETAILED DESCRIPTION

[0021] The embodiment of the present application discloses a sealing structure of a polymerization kettle. By pressing the pressure ring 18 on the kettle cover 102 against the top surface of the intermediate ring 15, the intermediate ring 15 will squeeze the rubber sealing ring 14. The deformation of the rubber sealing ring 14 will fill the gap between the intermediate ring 15 and the upper groove 111, thereby playing a sealing role. The outer rubber ring 16 inserted on the outer wall of the intermediate ring 15 will conflict with the side wall of the upper groove 111, and the inner rubber ring 17 inserted on the inner wall of the intermediate ring 15 will conflict with the outer wall of the ring cylinder 13. The inner rubber ring 17 and the outer rubber ring 16 will conflict with each other. The rubber ring 16 seals part of the area between the kettle cover 102 and the kettle body 101. In addition, the sealing oil is filled between the two adjacent inner ring strips 171 on the inner rubber ring 17 and the ring tube 13, and between the two adjacent outer ring strips 161 on the outer rubber ring 16 and the side wall of the upper groove 111. The use of sealing oil can further improve the sealing effect of the inner rubber ring 17 and the outer rubber ring 16, achieve multiple seals, hinder the outflow of tiny chemical substances in the airflow, and reduce chemical damage to external personnel.

[0022] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0023] Reference Figures 1 to 4 As shown, a sealing structure for a polymerization kettle includes a seat ring 11, a side skirt ring 12, a ring barrel 13, a rubber sealing ring 14, an intermediate ring 15, an outer rubber ring 16, an inner rubber ring 17, and a pressure ring 18. The seat ring 11 is annular and is integrally formed on the top surface of the kettle body 101. The outer diameter of the seat ring 11 is larger than the outer diameter of the kettle body 101, the inner diameter of the seat ring 11 is consistent with the inner diameter of the kettle body 101, and the top surface of the seat ring 11 is flat.

[0024] The side skirt ring 12, the ring tube 13 and the pressure ring 18 are all integrally formed at the edge of the kettle cover 102. The side skirt ring 12 is an annular plate. The side skirt ring 12 is integrally formed at the edge of the kettle cover 102. The outer diameter of the side skirt ring 12 is consistent with the outer diameter of the seat ring 11. When the kettle cover 102 is covered on the kettle body 101, the side skirt ring 12 is horizontal and located on the top surface of the seat ring 11. A number of mounting through holes 121 are opened along the circumference of the side skirt ring 12. The mounting through holes 121 pass through the upper and lower surfaces of the side skirt ring 12. The through holes 121 are evenly spaced around the circumference of the side skirt ring 12. A plurality of upright posts 103 are vertically fixed to the top surface of the seat ring 11. The number of upright posts 103 is the same as the number of mounting through holes 121. The upright posts 103 are evenly spaced around the circumference of the seat ring 11. Threaded grooves are provided on the top and bottom of the upright posts 103. The upright posts 103 pass through the mounting through holes 121 of the side skirt ring 12. Locking nuts 104 are abutted on the upper and lower surfaces of the side skirt ring 12. The locking nuts 104 are threadedly connected to the upright posts 103. After the kettle cover 102 is opened, the kettle cover 102 can be moved upward. After the side skirt ring 12 of the kettle cover 102 is moved horizontally to the top of the upright posts 103, the locking nuts 104 on the upper and lower surfaces of the side skirt ring 12 can be locked to the upper and lower surfaces of the side skirt ring 12, so that the kettle cover 102 can stay on the top of the upright posts 103.

[0025] The ring cylinder 13 is a short cylindrical shape and is integrally formed on the bottom surface of the kettle cover 102. The height of the ring cylinder 13 is longer than the height of the inner rubber ring 17. When the pressure ring 18 is in contact with the intermediate ring 15, the bottom surface of the ring cylinder 13 is located below the bottom surface of the inner rubber ring 17. When the kettle cover 102 is covered on the kettle body 101, the outer wall of the ring cylinder 13 is in contact with the inner wall of the kettle body 101; the pressure ring 18 is ring-shaped and is integrally formed between the side skirt ring 12 and the ring cylinder 13. The outer diameter of the pressure ring 18 is smaller than the outer diameter of the side skirt ring 12, and the pressure ring 18 is horizontal.

[0026] Reference Figure 5An upper groove 111 is provided on the inner wall of the seat ring 11. The upper groove 111 is opened along the circumference of the seat ring 11 and is communicated with the top surface of the seat ring 11. The rubber sealing ring 14 is used to be placed in the upper groove 111. A lower groove 112 is provided at the bottom of the upper groove 111. The lower groove 112 is opened along the circumference of the seat ring 11. The groove width of the lower groove 112 is smaller than the groove width of the upper groove 111, and the lower groove 112 is communicated with the inner wall of the seat ring 11, and the rubber sealing ring 14 is located above the lower groove 112.

[0027] Continue to refer to Figure 5 , the middle ring 15 is placed in the upper groove 111. The middle ring 15 is a ring-shaped rubber. An outer slot 151 is provided on the outer circumference of the middle ring 15. The outer slot 151 is opened along the circumference of the middle ring 15. An outer rubber ring 16 is inserted into the outer slot 151. The cross section of the outer rubber ring 16 is T-shaped. There is an interference fit between the outer rubber ring 16 and the outer slot 151. A plurality of outer ring strips 161 are formed on the side of the outer rubber ring 16 away from the outer slot 151. The plurality of outer ring strips 161 are distributed at equal intervals along the height direction of the outer rubber ring 16. When the middle ring 15 is placed in the upper groove 111, the outer ring strips 161 abuts against the groove wall of the upper groove 111; an inner slot 152 is provided on the inner circumferential surface of the intermediate ring 15, and the inner slot 152 is opened along the circumference of the intermediate ring 15. An inner rubber ring 17 is inserted into the inner slot 152, and the cross-section of the inner rubber ring 17 is T-shaped. There is an interference fit between the inner rubber ring 17 and the inner slot 152. A plurality of inner ring strips 171 are formed on the side surface of the inner rubber ring 17 away from the inner slot 152. The plurality of inner ring strips 171 are distributed at equal intervals along the height direction of the inner rubber ring 17. When the intermediate ring 15 is placed in the upper groove 111, the inner ring strips 171 abut against the outer wall of the ring cylinder 13.

[0028] Therefore, when the kettle cover 102 is placed on the kettle body 101, the pressure ring 18 can press down the intermediate ring 15, and the intermediate ring 15 will enter the upper groove 111. The intermediate ring 15 will press down the rubber sealing ring 14, and the outer rubber ring 16 inserted on the outer wall of the intermediate ring 15 will conflict with the side wall of the upper groove 111, and the inner rubber ring 17 inserted on the inner wall of the intermediate ring 15 will conflict with the ring tube 13. Therefore, the rubber sealing ring 14, the inner rubber ring 17 and the outer rubber ring 16 all achieve a sealing effect.

[0029] Continue to refer to Figure 5The bottom surface of the intermediate ring 15 is integrally formed with a lower ring 153. The width of the lower ring 153 is smaller than that of the intermediate ring 15. The lower ring 153 is close to the inner edge of the intermediate ring 15. The lower ring 153 is used to be placed in the lower groove 112. The bottom surface of the lower ring 153 is provided with a plurality of mounting countersunk holes 1531. The plurality of mounting countersunk holes 1531 are evenly distributed along the circumference of the lower ring 153. A spring 19 is arranged in the mounting countersunk hole 1531. One end of the spring 19 is fixed to the bottom surface of the mounting countersunk hole 1531, and the other end is fixed to the bottom of the lower groove 112. When the spring 19 is in a non-stressed state, the intermediate ring 15 is separated from the rubber sealing ring 14. Therefore, when the kettle cover 102 is separated from the kettle body 101, the intermediate ring 15 will move upward under the action of the spring 19, so that the intermediate ring 15 will be separated from the rubber sealing ring 14, thereby achieving a contact sealing effect. Moreover, under the connection of the spring 19, the intermediate ring 15 can be prevented from completely separating from the upper groove 111.

[0030] Reference Figure 5 , a horizontal guide hole 181 is provided on the outer circumferential surface of the pressure ring 18, and the guide horizontal hole 181 is a circular hole. There are multiple guide horizontal holes 181, and the multiple guide horizontal holes 181 are evenly distributed along the week of the pressure ring 18. The diameter line of the guide horizontal hole 181 is collinear with the diameter line of the pressure ring 18, and a vertical guide vertical hole 182 is provided on the lower surface of the pressure ring 18. The guide vertical hole 182 is a circular hole. There are several guide vertical holes 182, and the number is consistent with the number of guide horizontal holes 181. There is a one-to-one correspondence between the several guide horizontal holes 181 and the several guide vertical holes 182. The guide vertical hole 182 is close to the outer wall of the ring tube 13, and the guide vertical hole 182 is connected to the guide horizontal hole 181. When the kettle cover 102 is placed on the kettle body 101, and the middle ring 15 is placed in the upper groove 111 and the rubber sealing ring 14 is compressed, a hose can be inserted into the guide horizontal hole 181 on the outside of the kettle cover 102, and the hose is used to transport sealing oil into the guide horizontal hole 181. The sealing oil can pass through the guide horizontal hole 181 and the guide vertical hole 182 in turn, and then the sealing oil finally flows into the space between the inner rubber ring 17 and the ring cylinder 13, so that the sealing oil can be filled between the two adjacent inner ring strips 171 on the inner rubber ring 17 and the ring cylinder 13. The use of sealing oil can further improve the sealing effect of the inner rubber ring 17. In addition, a hose can be inserted into the gap between the side skirt ring 12 and the seat ring 11, which can be used to softly transport sealing oil to the gap between the outer rubber ring 16 and the side wall of the upper groove 111, so that the gap between two adjacent outer ring strips 161 on the outer rubber ring 16 and the side wall of the upper groove 111 is filled with sealing oil, thereby further improving the sealing effect of the outer rubber ring 16.

[0031] In addition, continue to refer to Figure 5As shown, a chamfered edge 1501 is provided at the edge of the top surface of the intermediate ring 15 close to the inner rubber ring 17. The chamfered edge 1501 is chamfered along a circle of the intermediate ring 15, and the top surface of the inner rubber ring 17 is located below the bottom edge of the chamfered edge 1501. Since the chamfered edge 1501 is provided, when the sealing oil can pass through the guide horizontal hole 181 and the guide vertical hole 182 in sequence and flow into the top of the inner rubber ring 17, the space formed by the chamfered edge 1501 can meet the storage needs of the sealing oil. Therefore, the sealing oil replenishment can be guaranteed for a long time, and the bottom surface of the pressure ring 18 and the outer wall of the ring cylinder 13 are filled with sealing oil over a large area, which can increase the sealing area, thereby further improving the sealing effect of the pressure ring 18 and the ring cylinder 13.

[0032] This application can explain its functional principles through the following operation methods:

[0033] When the kettle cover 102 is placed on the kettle body 101, the kettle cover 102 is moved downward along the vertical direction of the column 103, and the pressure ring 18 on the kettle cover 102 is pressed against the top surface of the intermediate ring 15. The intermediate ring 15 is continuously pressed down by the pressure ring 18, so that the intermediate ring 15 can enter the upper groove 111. At this time, the spring 19 in the lower ring 153 of the intermediate ring 15 is in a compressed state. After the intermediate ring 15 enters the groove, the intermediate ring 15 squeezes the rubber sealing ring 111. 4. The deformation of the rubber sealing ring 14 will fill the gap between the middle ring 15 and the upper groove 111, playing a sealing role. At this time, the lower ring 153 will enter the lower groove 112, and the outer rubber ring 16 inserted on the outer wall of the middle ring 15 will conflict with the side wall of the upper groove 111, and the inner rubber ring 17 inserted on the inner wall of the middle ring 15 will conflict with the outer wall of the ring tube 13. The inner rubber ring 17 and the outer rubber ring 16 also achieve sealing for part of the area between the kettle cover 102 and the kettle body 101.

[0034] Then, the locking nut 104 on the upper surface of the side skirt ring 12 can be used to lock the kettle cover 102 downward. After locking the kettle cover 102, the sealing oil can be transported into the guide horizontal hole 181 using a hose. The sealing oil can pass through the guide horizontal hole 181 and the guide vertical hole 182 in turn, and then the sealing oil finally flows into the space between the inner rubber ring 17 and the ring cylinder 13, and the sealing oil can be filled between the two adjacent inner ring strips 171 on the inner rubber ring 17 and the ring cylinder 13. Then, a hose is inserted into the gap between the side skirt ring 12 and the seat ring 11. The hose can transport the sealing oil to the space between the outer rubber ring 16 and the side wall of the upper groove 111, and the sealing oil can be filled between the two adjacent outer ring strips 161 on the outer rubber ring 16 and the side wall of the upper groove 111. The sealing oil can be used to further improve the sealing effect of the inner rubber ring 17 and the outer rubber ring 16. As described above, multiple seals are achieved between the kettle cover and the kettle body, which blocks the outflow of tiny chemical substances in the air flow and reduces chemical damage to external workers.

[0035] When the kettle cover 102 is opened, the kettle cover 102 can be translated upward, and then the side skirt ring 12 of the kettle cover 102 can be translated to the top of the column 103, and the locking nuts 104 on the upper and lower surfaces of the side skirt ring 12 can be locked on the upper and lower surfaces of the side skirt ring 12, so that the kettle cover 102 can stay on the top of the column 103, and when the kettle cover 102 is separated from the kettle body 101, under the action of the spring 19, the intermediate ring 15 will move upward, so that the intermediate ring 15 will be separated from the rubber sealing ring 14, thereby achieving a contact sealing effect.

[0036] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

[0037] The above is only a preferred specific implementation method of the embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solution and concept of the present application within the technical scope disclosed in the present application, and they should be covered by the scope of protection of the present application.

Claims

1. A sealing structure for a polymerization reactor, characterized in that: The invention comprises a seat ring (11) integrally formed at the edge of the top opening of the kettle body (101), a side skirt ring (12) integrally formed at the outer edge of the kettle cover (102) and in a horizontal shape, and a ring cylinder (13) integrally formed at the inner edge of the kettle cover (102) and in a vertical shape, wherein an upper groove (111) communicating with the top surface of the seat ring (11) is provided on the inner wall of the seat ring (11), a rubber sealing ring (14) is placed in the upper groove (111), and the upper side of the rubber sealing ring (14) contacts the upper surface of the seat ring (11). An intermediate ring (15) is provided, an outer slot (151) is provided on the outer wall of the intermediate ring (15), an inner slot (152) is provided on the inner wall of the intermediate ring (15), an outer rubber ring (16) is inserted into the outer slot (151), an inner rubber ring (17) is inserted into the inner slot (152), a pressure ring (18) is formed between the side skirt ring (12) and the ring cylinder (13), and the pressure ring (18) is used to abut against the top surface of the intermediate ring (15); A plurality of equally spaced mounting through holes (121) are provided along a circumference of the side skirt ring (12); a plurality of equally spaced upright posts (103) are vertically fixed to the top surface of the seat ring (11); the upright posts (103) pass through the mounting through holes (121); locking nuts (104) are abutted on the upper and lower surfaces of the side skirt ring (12); the locking nuts (104) are threadedly connected to the upright posts (103); The bottom of the upper groove (111) is provided with a lower groove (112), the lower groove (112) is located below the upper groove (111), the top surface of the lower groove (112) is connected to the upper groove (111), and the bottom surface of the intermediate ring (15) is integrally formed with a lower ring (153), and the lower ring (153) is used to abut against the lower groove (112); The bottom surface of the lower ring (153) is provided with a plurality of mounting countersunk holes (1531), and the plurality of mounting countersunk holes (1531) are evenly distributed along a circumference of the lower ring (153). A spring (19) is provided in the mounting countersunk hole (1531), one end of the spring (19) is fixed to the bottom surface of the mounting countersunk hole (1531), and the other end is fixed to the bottom of the lower groove (112). When the spring (19) is in a non-stressed state, the intermediate ring (15) is separated from the rubber sealing ring (14); A plurality of outer ring strips (161) are formed on a side surface of the outer rubber ring (16) away from the outer slot (151), and the plurality of outer ring strips (161) are distributed at equal intervals along the height direction of the outer rubber ring (16). The outer ring strips (161) are used to abut against the groove wall of the upper groove (111). A plurality of inner ring strips (171) are formed on a side surface of the inner rubber ring (17) away from the inner slot (152), and the plurality of inner ring strips (171) are distributed at equal intervals along the height direction of the inner rubber ring (17). The inner ring strips (171) are used to abut against the outer wall of the ring cylinder (13). A horizontal guide hole (181) is provided on the outer peripheral surface of the pressure ring (18), and a vertical guide hole (182) is provided on the lower surface of the pressure ring (18). The guide hole (182) is close to the outer wall of the ring cylinder (13). The guide hole (182) and the guide hole (181) are connected to each other. The guide hole (181) is used to introduce sealing oil.

2. A sealing structure for a polymerization reactor as claimed in claim 1, characterized in that: A chamfered right-angled edge (1501) is provided at the edge of the top surface of the intermediate ring (15) close to the inner rubber ring (17), and the top surface of the inner rubber ring (17) is located below the bottom edge of the chamfered right-angled edge (1501).

3. A sealing structure for a polymerization reactor as claimed in claim 1, characterized in that: The height of the ring cylinder (13) is longer than the height of the inner rubber ring (17), and when the pressure ring (18) is in contact with the intermediate ring (15), the bottom surface of the ring cylinder (13) is located below the bottom surface of the inner rubber ring (17).

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