A type of oil well polished rod seal

Abstract

This utility model relates to the field of oil extraction equipment technology, specifically a sucker well polished rod seal, including a packing cavity, a main packing gland within the packing cavity, and a piston cavity within the lower part of the main packing gland. A piston assembly is located within the piston cavity, positioned below the main packing gland. The lower part of the piston cavity is connected to an inlet pipe and an outlet pipe that penetrate the packing cavity. This utility model allows external pressurized liquid to be introduced through the inlet pipe, which drives a multi-stage ejector piston to rise step by step, automatically ejecting the main packing gland from the packing cavity, avoiding the tedious manual removal of the packing gland. This structure greatly simplifies the packing replacement process, lowers the operational threshold and labor intensity, significantly shortens the operation time for single-well packing replacement, thereby reducing pumping unit downtime for maintenance and minimizing crude oil production losses caused by equipment maintenance, effectively ensuring continuous and stable oil well production.

Description

Technical Field

[0001] This utility model relates to the field of oil extraction equipment technology, specifically a sucker rod seal for oil wells. Background Technology

[0002] In oilfield production, underground crude oil is extracted by surface pumping units through sucker rods (with polished rods at the top) that drive downhole pumps. Each wellhead is equipped with a polished rod sealer to prevent oil leakage. Its basic components include a body installed on the wellhead, with a cylindrical cavity inside the body that holds sealing packing. Several annular sealing packings are filled in this cavity. A pressure cap is usually installed above the sealing packings. Axial pressure is applied by fastening bolts, causing the sealing packings to expand radially and tightly wrap around the polished rod surface, thereby achieving a seal between the polished rod and the sealer body.

[0003] Frequent reciprocating movement of the polished rod causes long-term wear on the sealing packing, leading to gaps between the sealing packing and the polished rod, resulting in leakage. In this case, the worn sealing packing needs to be replaced. The polished rod seal contains at least five to seven sealing packings, which are tightly fitted between the cylindrical cavity and the polished rod for sealing. Replacement requires prying them out one by one, a time-consuming and labor-intensive process due to the tight fit between the sealing packings and the polished rod and cavity. Packing replacement must be performed after the pumping unit is shut down, which not only affects normal crude oil production but also increases the workload of production personnel.

[0004] In addition, when the sealing packing is replaced, there is no longer a sealing structure between the polished rod and the cylindrical cavity, which can easily lead to oil and gas leakage and cause pollution to the surrounding environment. Utility Model Content

[0005] The technical problem to be solved by this utility model is to overcome the defects of the prior art and provide a polished rod seal for oil wells.

[0006] To solve the above-mentioned technical problems, this utility model provides the following technical solution: A sucker well polished rod seal includes a packing cavity, a main packing is disposed within the packing cavity, a piston cavity is disposed within the packing cavity below the main packing, a piston assembly is disposed within the piston cavity, the piston assembly is disposed below the main packing, and an inlet pipe and an outlet pipe that penetrate the packing cavity are respectively connected to the lower part of the piston cavity.

[0007] In the above structure, the inlet pipe is used to connect to external pressurized liquid. The hydraulic power is used to push the piston assembly to rise, thereby enabling the piston assembly to push the main packing to rise and push the main packing out of the packing cavity. This makes the replacement of the main packing convenient and quick, which not only improves work efficiency but also shortens the downtime of the pumping unit and avoids affecting the normal production of crude oil.

[0008] The lower part of the packing cavity is provided with a first light rod through hole, and a limit tube is fixedly connected to the inner wall of the first light rod through hole. The piston assembly can slide between the outer wall of the limit tube and the inner wall of the packing cavity.

[0009] The piston assembly includes at least two stages of ejector pistons, and the ejector pistons are annular structures. Among them, the ejector piston close to the inner wall of the packing cavity is the initial ejector piston. The outer wall of the initial ejector piston is slidably connected to the inner wall of the packing cavity, and a sealing assembly is provided between the two. A connecting ring is provided on the lower inner wall of the initial ejector piston. The remaining ejector pistons are provided with connecting rings on their inner and outer walls. The connecting rings on the inner and outer walls are respectively located at the top and bottom of the ejector piston. When pushed by hydraulic power, two adjacent ejector pistons can be connected by the connecting rings. A sealing assembly is provided between two adjacent ejector pistons. A connecting ring is provided on the upper outer side of the limiting tube. The ejector piston, which is slidably sleeved on the outside of the limiting tube, can be engaged with the connecting ring of the limiting tube through the connecting ring at the bottom, thereby limiting the maximum rising distance of the piston assembly. A sealing assembly is provided between the limiting tube and the ejector piston.

[0010] The sealing components mentioned above can be made using sealing rings.

[0011] The inlet of the liquid inlet pipe into the piston chamber is located at the lower part of the initial ejection piston. When pressurized liquid is introduced, the initial ejection piston is the first to move.

[0012] The inlet pipe is equipped with a check valve, and the outlet pipe is equipped with a pressure relief valve to control the entry and exit of pressurized liquid.

[0013] The oil well polished rod sealer also includes a base, which is located below the packing cavity. A second polished rod passage hole is opened in the middle of the base, and a fixing seat is fixedly installed on the upper part of the base. Both the base and the fixing seat are annular structures. An auxiliary packing is installed inside the fixing seat and is located on the upper part of the base. An axial compression mechanism is installed on the upper part of the auxiliary packing. The axial compression mechanism can compress the auxiliary packing. When the main packing is replaced, the auxiliary packing is compressed to seal the polished rod and prevent oil and gas leakage.

[0014] The axial compression mechanism includes a movable pressure plate, which is fixedly connected to the bottom of the packing cavity. A third guide rod through hole is provided in the middle of the movable pressure plate. The movable pressure plate is located on the upper part of the auxiliary packing, and its lower structural contour is adapted to the upper contour of the auxiliary packing, enabling it to compress the auxiliary packing. An inner tube is fixedly connected to the outside of the fixed base. A raised ring is provided at the bottom of the movable pressure plate, and the raised ring is slidably disposed between the inner tube and the auxiliary packing. An outer tube is fixedly sleeved on the outside of the movable pressure plate, and a driving mechanism is connected to the lower part of the outer tube to drive the outer tube to descend.

[0015] The driving mechanism includes an adjusting nut, which is configured as a stepped ring structure. The lower end of the adjusting nut is rotatably sleeved on the outside of the base. An annular gap is provided between the upper end of the adjusting nut and the base. A spring is installed in the gap. The lower end of the outer tube is slidably sleeved on the outer wall of the base, and the bottom surface of the outer tube is in contact with the spring. The inner wall of the adjusting nut is threadedly connected to the outer wall of the outer tube.

[0016] The base has an annular groove on its outside. Two semi-circular limiting rings are inserted into the annular groove. The limiting rings protrude from the outer wall of the base and are set on the step of the adjusting nut, thereby restricting the upward movement of the adjusting nut. A spring is set on the upper surface of the limiting ring.

[0017] The main packing has a disc at the top and a tray at the bottom. The disc is located below the pressure cap and the tray is located above the piston assembly. Both the disc and the tray have through holes in the middle. A pressure cap is provided at the top of the packing cavity, and the pressure cap is threadedly connected to the top of the packing cavity.

[0018] The beneficial effects achieved by this utility model are: 1. This utility model connects to external pressurized liquid through an inlet pipe, which drives a multi-stage ejection piston to rise step by step, automatically ejecting the main packing from the packing cavity, thus avoiding the tedious manual removal of the packing. This structure greatly simplifies the packing replacement process, lowers the operational threshold and labor intensity, significantly shortens the operation time for single-well packing replacement, thereby reducing pumping unit downtime for maintenance and minimizing crude oil production losses caused by equipment maintenance, effectively ensuring continuous and stable oil well production.

[0019] 2. This utility model can eliminate oil and gas leakage during replacement operations and avoid environmental pollution problems: This utility model adds an auxiliary packing and a matching axial compression mechanism to the base position. During the disassembly and replacement of the main packing, the auxiliary packing can continuously seal the polished rod, effectively blocking the oil and gas leakage channel, solving the oil and gas leakage problem in packing replacement operations, avoiding environmental pollution risks, and meeting the requirements of green and safe production in oil fields.

[0020] 3. This utility model employs a piston assembly consisting of at least two stages of annular ejector pistons. A connecting ring ensures precise engagement between adjacent pistons. Simultaneously, the connecting ring of the limiting tube restricts the maximum upward distance of the piston assembly, allowing for precise control of the main packing ejection stroke and preventing over- or under-ejection. Sealing components are installed at each piston mating position, between the piston and the packing cavity, and between the limiting tube, ensuring the hydraulic system's sealing performance, stable hydraulic power output, smooth and reliable ejection operation, and a low equipment failure rate.

[0021] 4. By installing a check valve in the inlet pipe and a pressure relief valve in the outlet pipe, this utility model can accurately control the entry and pressure relief of pressurized liquid, realize the controllable operation of piston ejection and reset, the operation process is simple and convenient, no complicated operation process is required, and it is suitable for routine maintenance operation scenarios in oilfields.

[0022] 5. The main packing of this utility model is equipped with a disc and a tray on the top and bottom, and with the top threaded cover, the main packing can be precisely limited and fixed, which improves the stability of the main sealing structure, extends the overall service life of the sealing packing, and reduces the frequency of maintenance and replacement. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a schematic diagram of the structure of this utility model (with the main packing gland being replaced). Figure 3 This is a schematic diagram of the structure of this utility model (in working condition).

[0024] In the diagram: 1. Pressure cap; 2. Disc; 3. Packing cavity; 4. Main packing; 5. Tray; 6. Liquid outlet pipe; 7. Pressure relief valve; 8. First polished rod through hole; 9. Moving pressure plate; 10. Outer tube; 11. Inner tube; 12. Adjusting nut; 13. Spring; 14. Limiting ring; 15. Base; 16. Third polished rod through hole; 17. Second polished rod through hole; 18. Sealing assembly; 19. Initial ejection piston; 20. Ejection piston; 21. Limiting tube; 22. Liquid inlet pipe; 23. One-way valve; 24. Auxiliary packing; 25. Fixing seat; 26. Oil wellhead; 27. Polished rod. Detailed Implementation

[0025] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0026] Example: like Figure 1 , Figure 3 As shown, a sucker well polished rod seal includes a packing cavity 3, within which five main packing rings 4 are arranged. A piston chamber is located within the packing cavity 3 at the lower part of each main packing ring 4. A piston assembly is installed within the piston chamber, positioned at the lower part of the main packing rings 4. The lower part of the piston chamber is connected to an inlet pipe 22 and an outlet pipe 6, both penetrating the packing cavity 3, for connecting pressurized fluid.

[0027] The main packing 4 has a disc 2 at its upper part and a tray 5 at its lower part. The disc 2 is located below the pressure cap 1, and its function is to prevent the pressure cap 1 from directly contacting the main packing 4, thus avoiding damage to it during tightening and compression. The tray 5 is located on the upper part of the piston assembly, and both the disc 2 and the tray 5 have through holes in their middle parts.

[0028] A pressure cap 1 is provided at the top of the packing cavity 3. A through hole is provided in the middle of the pressure cap 1, and the pressure cap 1 is threadedly connected to the top of the packing cavity 3.

[0029] Specifically, a first guide rod through hole 8 is provided at the lower part of the packing cavity 3. A limiting tube 21 is fixedly connected to the inner wall of the first guide rod through hole 8 by means of a threaded connection. The piston assembly can slide between the outer wall of the limiting tube 21 and the inner wall of the packing cavity 3. The piston cavity is formed between the outer wall of the limiting tube 21 and the inner wall of the packing cavity 3.

[0030] The piston assembly includes two-stage ejector pistons 20, which are interlocking annular structures. The initial ejector piston 19 is located close to the inner wall of the packing cavity 3. The outer wall of the initial ejector piston 19 is slidably connected to the inner wall of the packing cavity 3, and a sealing assembly 18 is provided between them. A connecting ring, which is a raised annular structure, is provided on the lower inner wall of the initial ejector piston 19.

[0031] Another ejector piston 20 has connecting rings on its inner and outer walls, respectively, located at the top and bottom of the ejector piston 20. Figure 2 As shown, when pushed by hydraulic power, two adjacent ejector pistons 20 can be connected by a connecting ring, thereby moving upward one by one. A sealing assembly 18 is provided between two adjacent ejector pistons 20.

[0032] The upper end of the limiting tube 21 is provided with a connecting ring. The ejector piston 20, which is slidably sleeved on the outside of the limiting tube 21, can be connected to the connecting ring of the limiting tube 21 through the connecting ring at the bottom. The limiting tube 21 is used to limit the maximum rising distance of the piston assembly. A sealing assembly 18 is provided between the limiting tube 21 and the ejector piston 20.

[0033] The sealing component 18 mentioned above can be a sealing ring.

[0034] The inlet pipe 22 is used to connect to external structures such as hydraulic pumps, thereby connecting pressurized liquid and using hydraulic power to push the piston assembly to rise, so that the piston assembly can push the main packing 4 to rise. When replacement is needed, the main packing 4 is pushed out of the packing cavity 3, making the replacement of the main packing 4 convenient and quick.

[0035] The inlet of the liquid inlet pipe 22 into the piston chamber is located at the lower part of the initial ejector piston 19, and a certain initial space is left between the lower part of the initial ejector piston 19 and the stepped surface of the packing cavity 3 to store a small amount of pressurized liquid. When pressurized liquid is introduced, the initial ejector piston 19 first moves upward.

[0036] A one-way valve 23 is installed on the inlet pipe 22, and a pressure relief valve 7 is installed on the outlet pipe 6 to control the entry and exit of pressurized liquid. When installing a new main packing 4, the pressure relief valve 7 is opened to release the liquid and depressurize the piston chamber.

[0037] This utility model also includes a secondary auxiliary seal. Specifically, the oil well polished rod sealer further includes a base 15, which is fixedly connected to the wellhead 26. The base 15 is located below the packing cavity 3, and a second polished rod through hole 17 is provided in the middle of the base 15. A fixing seat 25 is fixedly installed on the upper part of the base 15. Both the base 15 and the fixing seat 25 are annular structures, and the fixing seat 25 and the base 15 are an integral structure. An auxiliary packing 24 is provided inside the fixing seat 25, and the auxiliary packing 24 is located on the upper part of the base 15, embedded between the base 15 and the fixing seat 25.

[0038] An axial compression mechanism is provided above the auxiliary packing 24. This mechanism compresses the auxiliary packing 24 during the replacement of the main packing 4, sealing the auxiliary packing 24 to prevent oil and gas leakage. The axial compression mechanism includes a movable pressure plate 9, which is fixedly connected to the bottom of the packing cavity 3. A third guide hole 16 is provided in the middle of the movable pressure plate 9. The movable pressure plate 9 is positioned above the auxiliary packing 24, and its lower structural contour matches the upper contour of the auxiliary packing 24, enabling it to compress the auxiliary packing 24.

[0039] The inner tube 11 is fixedly connected to the outside of the fixed base 25 by a threaded connection. A raised ring is provided at the bottom of the movable pressure plate 9, and the raised ring is slidably disposed between the inner tube 11 and the auxiliary packing 24. A gap is left between the raised ring and the fixed base 25. An outer tube 10 is fixedly sleeved to the outside of the movable pressure plate 9 by a threaded connection. A drive mechanism is connected to the lower part of the outer tube 10 to drive the outer tube 10 to descend.

[0040] The driving mechanism includes an adjusting nut 12, which is configured as a stepped ring structure with a stepped surface on the inner side. The lower end of the adjusting nut 12 is rotatably sleeved on the outside of the base 15, and an annular gap is provided between the upper end of the adjusting nut 12 and the base 15. Multiple springs 13 are installed in the gap. The lower end of the outer tube 10 is slidably sleeved on the outer wall of the base 15, and the bottom surface of the outer tube 10 contacts the springs 13. The inner wall of the adjusting nut 12 is threadedly connected to the outer wall of the outer tube 10. When the adjusting nut 12 is rotated, the outer tube 10 can overcome the reverse force of the springs 13 and move downward, thereby driving the moving pressure plate 9 to squeeze the auxiliary packing 24, causing the auxiliary packing 24 to deform and press against the surface of the smooth rod 27 for sealing.

[0041] The zero point position is marked on the lower outer wall of the outer tube 10. When the top surface of the adjusting nut 12 is flush with this position, it indicates that the moving pressure plate 9 has left the auxiliary packing 24 and is no longer pressing it.

[0042] The base 15 has an annular groove on its outer surface. Two semi-circular limiting rings 14 are inserted into the annular groove, and the two semi-circular limiting rings 14 can be assembled into a ring that mates with the annular groove. The limiting rings 14 protrude from the outer wall surface of the base 15 and are positioned on the stepped surface of the adjusting nut 12, thus restricting the upward movement of the adjusting nut 12. A spring 13 is positioned on the upper surface of the limiting rings 14, and the spring 13 provides upward support to the outer tube 10 above it. The outer tube 10 is connected to the adjusting nut 12, thus also providing upward support to the adjusting nut 12, causing the stepped surface of the adjusting nut 12 to engage with the limiting rings 14, thereby restricting the adjusting nut 12 to rotate only relative to the base 15.

[0043] The polished rod 27 passes through the through hole of the pressure cap 1, the through hole of the disc 2, the main packing 4, the through hole of the tray 5, the limiting tube 21, the first polished rod through hole 8, the third polished rod through hole 16, the auxiliary packing 24 and the second polished rod through hole 17 from top to bottom before entering the oil well.

[0044] In accordance with existing technical specifications, sealing rings are selectively provided at the joints of each component of this utility model to ensure the overall sealing performance of the structure.

[0045] The following is a brief description of two working scenarios for the initial installation and packing replacement of this utility model: First working scenario, initial installation: Insert the utility model downwards through the upper end of the smooth rod 27, connect and fix the base 15 to the wellhead 26, first unscrew the pressure cap 1 at the upper end of the packing cavity 3 and take it out along with the disc 2, then insert the main packing 4 one by one into the packing cavity 3 (two semi-circular packings are a group, and a bevel needs to be cut on the whole circular packing), so that the main packing 4 is tightly stuck between the smooth rod 27 and the packing cavity 3, place the disc 2 on top of the main packing 4, and then tighten the pressure cap 1 to the packing cavity 3, so that the disc 2 presses down on the main packing 4 and seals the smooth rod 27.

[0046] The second working scenario, packing replacement: When replacing the main packing 4, the polished rod 27 needs to be sealed in advance through the secondary auxiliary seal. Specifically, first rotate the adjusting nut 12 and manually fix the outer tube 10 from the outside so that it cannot rotate. Since the adjusting nut 12 can only rotate relative to the base 15, when the adjusting nut 12 rotates, the outer tube 10 moves linearly and presses the spring 13 downward. The outer tube 10 drives the moving pressure plate 9 to descend, and the moving pressure plate 9 squeezes the auxiliary packing 24 to seal the polished rod 27. like Figure 2 As shown, then, open the pressure cap 1, take out the disc 2, connect a small piston or pressure pump or other filling device at the liquid inlet pipe 22, inject hydraulic oil into the piston chamber through the filling device, first push the initial ejector piston 19 to rise, after the initial ejector piston 19 rises, it drives the adjacent ejector piston 20 to rise through the connecting ring, thereby achieving step-by-step rise, and the rising piston assembly ejects the main packing 4 out of the packing chamber 3 one by one; When filling new packing, first open the pressure relief valve 7 so that the piston assembly can fall back when pressing down the new packing. Then, insert the new main packing 4 into the packing cavity 3 one by one, then put the disc 2 into the packing cavity 3, and then tighten the pressure cap 1 so that the disc 2 squeezes the packing to seal the polished rod 27. After the packing is replaced, close the pressure relief valve 7, remove the filling device, and then rotate the adjusting nut 12 to move the outer tube 10 upward. The reaction force of the spring 13 further causes it to rebound upward, thereby driving the moving pressure plate 9 to rise. The auxiliary packing 24 no longer squeezes the polished rod 27, and its seal on the polished rod 27 is released.

Claims

1. A sucker well polished rod seal, comprising a packing cavity (3), wherein a main packing (4) is disposed within the packing cavity (3), characterized in that, A piston chamber is provided in the packing cavity (3) at the lower part of the main packing (4), and a piston assembly is provided in the piston chamber. The piston assembly is located at the lower part of the main packing (4), and the lower part of the piston chamber is connected to an inlet pipe (22) and an outlet pipe (6) that pass through the packing cavity (3).

2. The oil well polished rod seal according to claim 1, characterized in that, The lower part of the packing cavity (3) is provided with a first light rod through hole (8), and a limit tube (21) is fixedly connected to the inner wall of the first light rod through hole (8). The piston assembly can slide between the outer wall of the limit tube (21) and the inner wall of the packing cavity (3).

3. The oil well polished rod seal according to claim 2, characterized in that, The piston assembly includes at least two stages of ejector pistons (20), and the ejector pistons (20) are annular structures; Among them, the initial ejection piston (19) is close to the inner wall of the packing cavity (3). The outer wall of the initial ejection piston (19) is slidably connected to the inner wall of the packing cavity (3), and a sealing assembly (18) is provided between them. A connecting ring is provided on the lower inner wall of the initial ejection piston (19). The inner and outer walls of the other ejector pistons (20) are respectively provided with connecting rings. The connecting rings of the inner and outer walls are respectively provided at the top and bottom of the ejector pistons (20). The two adjacent ejector pistons (20) are connected by connecting rings. A sealing assembly (18) is provided between the two adjacent ejector pistons (20). The upper end of the limiting tube (21) is provided with a connecting ring. The ejector piston (20) is slidably sleeved on the outside of the limiting tube (21). It can be connected to the connecting ring of the limiting tube (21) through the connecting ring at the bottom. A sealing assembly (18) is provided between the limiting tube (21) and the ejector piston (20).

4. The oil well polished rod seal according to claim 3, characterized in that, The inlet of the liquid inlet pipe (22) into the piston chamber is located at the lower part of the initial ejection piston (19).

5. The oil well polished rod seal according to claim 1, characterized in that, A one-way valve (23) is installed on the inlet pipe (22), and a pressure relief valve (7) is installed on the outlet pipe (6).

6. The oil well polished rod seal according to claim 1, characterized in that, It also includes a base (15), which is located below the packing cavity (3). A second light rod through hole (17) is provided in the middle of the base (15). A fixed seat (25) is fixedly provided on the upper part of the base (15). Both the base (15) and the fixed seat (25) are annular structures. An auxiliary packing (24) is provided on the inner side of the fixed seat (25). The auxiliary packing (24) is located on the upper part of the base (15). An axial compression mechanism is provided on the upper part of the auxiliary packing (24).

7. The oil well polished rod seal according to claim 6, characterized in that, The axial compression mechanism includes a movable pressure plate (9), which is fixedly connected to the bottom of the packing cavity (3). A third light rod through hole (16) is provided in the middle of the movable pressure plate (9). The movable pressure plate (9) is located on the upper part of the auxiliary packing (24). An inner tube (11) is fixedly connected to the outside of the fixed seat (25). A protruding ring is provided at the bottom of the movable pressure plate (9), and the protruding ring is slidably located between the inner tube (11) and the auxiliary packing (24). An outer tube (10) is fixedly sleeved on the outside of the movable pressure plate (9), and a driving mechanism is connected to the lower part of the outer tube (10).

8. The oil well polished rod seal according to claim 7, characterized in that, The driving mechanism includes an adjusting nut (12), which is configured as a stepped ring structure. The lower end of the adjusting nut (12) is rotatably sleeved on the outside of the base (15). An annular gap is provided between the upper end of the adjusting nut (12) and the base (15). A spring (13) is installed in the gap. The lower end of the outer tube (10) is slidably sleeved on the outer wall of the base (15), and the bottom surface of the outer tube (10) is in contact with the spring (13). The inner wall of the adjusting nut (12) is threadedly connected to the outer wall of the outer tube (10).

9. The oil well polished rod seal according to claim 8, characterized in that, The base (15) has an annular groove on its outside. Two semi-circular limiting rings (14) are inserted into the annular groove. The limiting rings (14) protrude from the outer wall of the base (15) and are set on the step of the adjusting nut (12). The spring (13) is set on the upper surface of the limiting rings (14).

10. The oil well polished rod seal according to claim 1, characterized in that, The main packing (4) is provided with a disc (2) at the top and a tray (5) at the bottom. The disc (2) is located at the bottom of the pressure cap (1), and the tray (5) is located at the top of the piston assembly. Both the disc (2) and the tray (5) have through holes in the middle. A pressure cap (1) is provided at the top of the packing cavity (3), and the pressure cap (1) is threadedly connected to the top of the packing cavity (3).

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