A thermal insulation joint for an injection-production integrated pipe column
By designing the thermal insulation joints for integrated pipe columns for injection and production, the thermal insulation layer between the inner and outer pipes and the actuator, the heat loss problem in heavy oil mining is solved, and the efficient combination of heat injection and mining is achieved. Reduce costs and improve mining effects.
Patent Information
- Application Number
- CN202210611889.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-05-31
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2042-05-31
AI Technical Summary
During heavy oil mining, two pipe strings are required through steam throughput, resulting in large heat loss, reducing the mining effect, and the heat loss is serious during the replacement of the pipe string, which affects the mining efficiency and cost.
A heat insulation joint for injection and production integrated pipe string is designed, including a heat insulation layer between the inner pipe and the outer pipe. The inner pipe is equipped with a heat injection channel and a production channel, and the channel is realized through the actuator and the control mechanism. Switch between them to ensure heat is retained and mined when needed.
The two process flows of heat injection and mining are realized in one pipe column, reducing mining costs, and ensuring the continuity and efficiency of the mining process through the thermal insulation layer.
Smart Images
Figure CN114856460B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of offshore heavy oil thermal recovery, and in particular relates to a thermal insulation joint for an injection-production integrated pipe column. Background Art
[0002] More than half of the billions of tons of proven reserves of oil in Bohai Oilfield are heavy oil. The development of heavy oil extraction technology plays an important role in the process of Bohai oil extraction. However, heavy oil products have the characteristics of high viscosity, high freezing point, poor fluidity and easy solidification. In the process of heavy oil extraction, the viscosity is reduced and its fluidity is increased by steam injection. This method requires the process of "heat injection-well soaking-oil extraction" and requires two trips of tubing. The first trip is for heat injection and the second trip is for extraction. However, the heat loss is large during the replacement of the tubing, which greatly reduces the extraction effect. Summary of the invention
[0003] In order to solve all or part of the above problems, the present invention aims to provide an insulating joint for an integrated injection and production pipe column, which can realize switching between two channels and can be used for two process flows of heat injection and production, saving production costs.
[0004] According to the present invention, there is provided a heat-insulating joint for an injection-production integrated pipe column, comprising an inner pipe and an outer pipe, wherein a heat-insulating layer is provided between the inner pipe and the outer pipe;
[0005] A heat injection channel and a production channel are provided in the inner tube, and the heat injection channel and the production channel are connected through a channel connection window;
[0006] An actuator is provided in the production channel. When the actuator is subjected to an action force, the actuator moves to a lower limit position in the production channel, and the production channel and the heat injection channel are not connected. The actuator is located above the lower limit position under normal conditions, and the production channel and the heat injection channel are connected.
[0007] The actuator is connected to a control mechanism, and the control mechanism can control the actuator to move to a lower limit position in the production channel.
[0008] Furthermore, the exterior of the inner tube is composed of multiple continuous eccentric circles, and two eccentric interfaces are respectively provided at the upper and lower ends of the inner tube, an upper eccentric interface and a lower eccentric interface are connected to form a heat injection channel, and another upper eccentric interface and another lower eccentric interface are connected to form a production channel.
[0009] Furthermore, the interior of the outer tube is provided with an eccentric circular hole that cooperates with the multiple continuous eccentric circles on the outside of the inner tube, the upper part of the outer tube is provided with two outer tube upper interfaces that cooperate with the eccentric interfaces at the upper end of the inner tube, the outer tube is inserted and cooperated with the inner tube, and the outer tube is provided with a cable channel.
[0010] Furthermore, the actuator includes a sealing head, the sealing head is threadedly connected to a lower valve body, the lower valve body is connected to the control mechanism, the lower valve body is sealed and connected to the production channel, a first expansion hole is provided at the production channel connected to the channel connecting window, the diameter of the first expansion hole is larger than the diameter of the production channel, the sealing head is located in the first expansion hole, and two reduction steps are formed between the first expansion hole and the production channel, wherein the upper first reduction step is the upper limit position of the sealing head movement, and the lower second reduction step is the lower limit position of the sealing head movement.
[0011] Furthermore, the lower end of the first expansion hole is connected to the production channel via the chamfer of the production channel, and the lower part of the sealing head is a conical structure that matches the chamfer of the production channel.
[0012] Furthermore, a second expansion hole is opened in the production channel above the first expansion hole, the lower valve body is located in the second expansion hole, and the lower valve body and the inner wall of the second expansion hole are sealed. A reset device is provided in the second expansion hole, and the reset device is connected to the lower valve body.
[0013] Furthermore, the reset device 1 includes a lower spring, which is arranged in the second expansion hole, and the upper end of the lower spring is connected to the lower valve body, and the lower end of the lower spring is connected to the bottom wall of the second expansion hole.
[0014] Furthermore, the inner tube at the upper part of the production channel is connected to a valve seat, the valve seat is connected to an upper joint, the upper joint is connected to a hydraulic pipeline, the control mechanism is arranged in the upper joint, and the control mechanism and the upper joint are sealed and connected.
[0015] Furthermore, the control mechanism includes a core shaft arranged in the upper joint, the lower end of the core shaft is connected to an upper valve body, the upper valve body is sealedly connected to the upper joint, and the upper valve body is connected to the lower valve body.
[0016] Furthermore, a second reset device is provided in the upper joint, and the second reset device is connected to the upper valve body.
[0017] Furthermore, the second resetting device includes an upper spring, which is sleeved on the core shaft. A positioning cap is fixedly connected to the upper joint. A hole is provided in the middle of the positioning cap for the core shaft to pass through. The positioning cap is connected to the upper end of the upper spring, and the upper valve body is connected to the lower end of the upper spring.
[0018] It can be seen from the above technical solution that the thermal insulation joint for the injection-production integrated pipe string provided by the present invention has the following beneficial effects:
[0019] The present invention can change the state between the production channel and the heat injection channel through the actuator, thereby realizing the two processes of mining and heat injection, and reducing the mining cost;
[0020] The present invention can protect other structures outside the thermal insulation joint by setting the thermal insulation layer;
[0021] The production channel and the heat injection channel of the present invention are connected under normal conditions, so even if the control mechanism fails, it will not affect the normal mining process. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 A cross-sectional view of a thermal insulation joint for an injection-production integrated pipe string according to an embodiment of the present invention;
[0023] Figure 2-3 This is a schematic structural diagram of a heat-insulating joint for an injection-production integrated pipe string according to an embodiment of the present invention;
[0024] Figure 4 It is a schematic diagram of a heat-insulating joint for an injection-production integrated pipe string in a heat-injection state according to an embodiment of the present invention;
[0025] Figure 5 It is a schematic diagram of a thermal insulation joint for an injection-production integrated pipe string in a production state according to an embodiment of the present invention;
[0026] The reference numerals in the figure are: hydraulic control pipeline 1, upper joint 2, positioning cap 3, upper spring 4, core shaft 5, upper valve body 6, valve seat 7, sealing chamber 8, lower valve body 9, lower spring 10, sealing head 11, inner tube 12, thermal insulation layer 13, outer tube 14, upper interface 101 of outer tube, cable channel 105, heat injection channel 201, production channel 202, upper interface 203 of heat injection channel, upper interface 204 of production channel, lower interface 205 of heat injection channel, lower interface 206 of production channel, channel connection window 207, first diameter reduction step 208, production channel chamfer 209, second diameter reduction step 210. DETAILED DESCRIPTION
[0027] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a thermal insulation joint for an injection-production integrated pipe string of the present invention in conjunction with the accompanying drawings.
[0028] like Figure 1-3 As shown, it is shown as an insulating joint for an injection-production integrated pipe column according to an embodiment of the present invention, comprising an inner pipe 12 and an outer pipe 14, an insulating layer 13 is provided between the inner pipe 12 and the outer pipe 14, the insulating layer 13 is composed of aerogel, aluminum foil or other insulating materials with radially equal wall thickness, and the setting of the insulating layer 13 can protect other structures outside the insulating joint during the injection-production process; a heat injection channel 201 and a production channel 202 are provided in the inner pipe 12, and the heat injection channel 201 and the production channel 202 are connected through a channel connection window 207, and an actuator is provided in the production channel 202, and the heat injection channel 201 and the production channel 202 can be connected or disconnected through the actuator, specifically The production channel 202 is provided with a channel for the actuator to move. When the actuator moves to the lower limit position in the channel after being acted upon by an external force, the production channel 202 and the heat injection channel 201 are not connected. At this time, the actuator can be used to inject high-temperature liquid through the heat injection channel 201. When the external force disappears, the actuator moves in the channel until it returns to a normal state. In the normal state, the actuator leaves the lower limit position in the channel, and the production channel 202 below the actuator is connected to the heat injection channel 201 through the channel connection window 207. At this time, it can be used for oil and gas production. The actuator is connected to a control mechanism, which is used to control the actuator to move from the normal state to the lower limit position in the production channel 202.
[0029] In the above embodiment, the outer portion of the inner tube 12 is composed of multiple sections of continuous eccentric circles, and there are two eccentric interfaces on the upper and lower parts of the inner tube 12, the upper part is the upper interface 203 of the heat injection channel and the upper interface 204 of the production channel, and the lower part is the lower interface 205 of the heat injection channel and the lower interface 206 of the production channel, and the upper interface 203 of the heat injection channel and the upper interface 204 of the production channel protrude beyond the upper plane of the inner tube 12, and the lower ends of the lower interface 205 of the heat injection channel and the lower interface 206 of the production channel are flush with the lower end of the inner tube 12, and the upper end of the heat injection channel is substantially parallel to the lower end of the inner tube 12. A connecting channel is formed between the upper interface 203 and the lower interface 205 of the heat injection channel, and the channel is the heat injection channel 201. A connecting production channel 202 is formed between the upper interface 204 of the production channel and the lower interface 206 of the production channel. The channel connection window 207 is connected between the production channel 202 and the heat injection channel 201. An insulating layer 13 is provided on the outside of the inner tube 12, and an outer tube 14 is provided on the outside of the insulating layer 13. The upper and lower ends of the inner tube 12 and the outer tube 14 are connected by welding and then vacuumed, so as to enhance the insulating effect of the insulating joint.
[0030] In the above embodiment, an eccentric circular hole is provided inside the outer tube 14 to cooperate with the multiple continuous eccentric circles outside the inner tube 12. Two outer tube upper interfaces 101 are provided on the upper part of the outer tube 14 to cooperate with the eccentric interfaces on the upper end of the inner tube 12. The outer tube 14 is inserted and matched with the inner tube 12. When installing, after the outer tube 14 is inserted downward into the inner tube 12 until the upper end of the inner tube 12, the outer tube upper interface 101 on the upper part of the outer tube 14 is just sleeved on the eccentric interface above the inner tube. The outer diameter profile of the outer tube is composed of a circle concentric with the center of the outer diameter profile size of the outer tube. A cable channel 105 is provided on the outer tube 14. The setting of the cable channel 105 makes it convenient to connect the cables required in the injection and production with the electrical equipment through the cable channel 105 when using the insulation joint for injection and production, which can fix the cables and protect the cables from damage.
[0031] On the basis of the above embodiment, the actuator in this embodiment includes a sealing head 11 and a lower valve body 9, the lower end of the lower valve body 9 is threadedly connected to the sealing head 11, the lower valve body 9 is sealed and connected to the production channel 202, and the lower valve body 9 is connected to the control mechanism, so when the lower valve body 9 is subjected to the pressure of the control mechanism, it can drive the sealing head 11 to move downward, and a first expansion hole is provided at the production channel 202, and the sealing head 11 is located in the first expansion hole, and the first expansion hole is the channel for the actuator movement mentioned above, and the first expansion hole is provided at the channel connection window 207, and the diameter of the first expansion hole It is larger than the diameter of the production channel 202, so two reduction steps are formed between the first expansion hole and the production channel 202 above and below it, wherein the upper first reduction step 208 is the upper limit position of the movement of the sealing head 11, and the lower second reduction step 210 is the lower limit position of the movement of the sealing head 11. When the sealing head moves to the lower limit position, the production channel 202 and the heat injection channel 201 are not connected. When the sealing head 11 is separated from the lower limit position and moves from the lower limit position to the upper limit position, the production channel 202 and the heat injection channel 201 are connected.
[0032] On the basis of the above embodiment, in this embodiment, the lower end of the first expansion hole is connected to the production channel 202 via the production channel chamfer 209, and the lower part of the sealing head 11 is a conical structure that matches the production channel chamfer 209. In this embodiment, the production channel chamfer 209 and the conical sealing head 11 cooperate to form a spherical-conical seal between the sealing head 11 and the production channel chamfer 209.
[0033] On the basis of the above embodiment, in the present embodiment, a second expansion hole is opened at the production channel 202 above the first expansion hole, the lower valve body 9 is located in the second expansion hole, and the lower valve body 9 and the inner wall of the second expansion hole are sealed. Since the lower valve body 9 and the inner wall of the second expansion hole are sealed, the lower valve body 9 can move downward along the second expansion hole when the pressure of the control mechanism is applied. In order to reset the lower valve body 9 after the pressure disappears, a reset device 1 is provided in the second expansion hole, and the reset device 1 is connected to the lower valve body 9. Therefore, when the pressure of the control mechanism disappears, the reset device 1 can drive the lower valve body 9 to reset.
[0034] On the basis of the above embodiment, the reset device 1 in this embodiment includes a lower spring 10, which is arranged in the second expansion hole, and the upper end of the lower spring 10 is connected to the lower valve body 9 in the second expansion hole, and the lower end of the lower spring 10 is connected to the bottom wall of the second expansion hole. Therefore, when the lower valve body 9 is subjected to the pressure of the control mechanism, the lower spring 10 can be compressed to move downward along the second expansion hole. When the pressure of the control mechanism disappears, the lower valve body 9 can move upward under the elastic force of the lower spring 10 to realize the reset of the lower valve body 9. The lower valve body 9 is reset to move upward with the sealing head 11.
[0035] On the basis of the above embodiment, in this embodiment, the upper production channel interface 204 at the upper part of the production channel 202 is connected with a valve seat 7, the upper part of the valve seat 7 is connected with the upper joint 2, the upper part of the upper joint 2 is connected with a hydraulic control line 1, the control mechanism is arranged in the upper joint 2, and the control mechanism and the upper joint 2 are sealed. In this embodiment, when liquid is injected into the space between the control mechanism and the upper joint 2 through the hydraulic control line 1, the control mechanism is subjected to pressure, and the control mechanism will push the sealing head 11 and the lower valve body 9 of the actuator to move downward under the action of the pressure, thereby achieving the purpose of controlling the movement of the actuator through the control mechanism. In this embodiment, the control of the control mechanism is achieved through the hydraulic control line 1, which has the advantage of convenient control.
[0036] On the basis of the above embodiments, the control mechanism in this embodiment includes a core shaft 5 arranged in the upper joint 2, and the lower end of the core shaft 5 is connected to the upper valve body 6, the upper valve body 6 is sealed with the upper joint 2, and the upper end of the lower valve body 9 is connected to the upper valve body 6 by a thread. In this embodiment, the upper valve body 6 is sealed with the upper joint 2. It can be seen from the previous embodiments that the lower valve body 9 and the inner wall of the second expansion hole are sealed, so a sealed cavity 8 is formed between the upper valve body 6, the upper joint 2, the lower valve body 9, the valve seat 7 and the inner tube 12. When liquid is injected into the space above the sealed cavity 8 through the hydraulic control pipeline 1, when the upper valve body 6 at the upper part of the sealed cavity 8 is subjected to the pressure of the liquid, the upper valve body 6 moves downward, thereby causing the sealed cavity 8 and the lower valve body 9 to move downward. When the lower valve body 9 moves downward to the second reducing step 210 below, the production channel 202 and the heat injection channel 201 can be disconnected.
[0037] On the basis of the above embodiment, in this embodiment, a second reset device is provided in the upper joint 2, and the second reset device is connected to the upper valve body 6. In this embodiment, after the liquid is discharged from the upper joint 2 through the hydraulic control line 1, the pressure on the upper valve body 6 disappears, and at this time, the second reset device can reset the upper valve body 6, and the reset of the upper valve body 6 drives the lower valve body 9 to move upward, and the production channel 202 is connected with the heat injection channel 201.
[0038] On the basis of the above embodiment, the second reset device in this embodiment includes an upper spring 4, which is sleeved on the core shaft 5, and a positioning cap 3 is fixedly connected to the upper joint 2. A hole is provided in the middle of the positioning cap 3 for the core shaft 5 to pass through, and the core shaft 5 can move up and down in the hole of the positioning cap 3. The lower end of the core shaft 5 passing through the hole of the positioning cap 3 is connected to the upper valve body 6, and the upper spring 4 is arranged between the positioning cap 3 and the upper valve body 6, and the positioning cap 3 is connected to the upper end of the upper spring 4, and the upper valve body 6 is connected to the lower end of the upper spring 4. In this embodiment, when liquid is injected into the upper joint 2 through the hydraulic control pipeline 1, the liquid presses the upper valve body 6 to overcome the upward pulling force of the upper spring 4 and move downward. When the liquid is discharged through the hydraulic control pipeline 1, the upper valve body 6 can be reset under the upward pulling force of the upper spring 4.
[0039] In order to facilitate understanding of the purpose of the invention of a thermal insulation joint for an integrated injection-production pipe string according to an embodiment of the present invention, the present embodiment is described in detail below.
[0040] The thermal insulation joint of the embodiment of the present invention can realize the two-trip process of heat injection and mining in one trip of the pipe string. When liquid is injected into the upper joint 2 through the hydraulic control pipeline 1, the upper valve body 6 and the sealing chamber 8 are subjected to the action of pressure. Under the action of pressure, the upper valve body 6 overcomes the rebound force of the upper spring 4 and moves downward. The downward movement of the upper valve body 6 drives the lower valve body 9 to overcome the rebound force of the lower spring 10 and move downward. The downward movement of the lower valve body 9 drives the sealing head 11 to move downward. When the sealing head 11 moves downward to the lower limit position, the sealing head 11 contacts the chamfer 209 of the production channel to form a spherical cone seal, such as Figure 4 As shown, at this time, the heat injection channel 201 is established, and heat injection can be carried out through the insulating joint. During the specific heat injection process, the high-temperature liquid required for heat injection enters the heat injection channel 201 from the upper interface 203 of the heat injection channel through the oil pipe, and then flows into the heat injection oil pipe from the lower interface 205 of the heat injection channel through the heat injection channel 201, and is injected into the formation through the heat injection oil pipe.
[0041] When the heat injection and well soaking are completed, the liquid in the upper joint 2 is discharged through the hydraulic control pipeline 1, and the pressure on the upper valve body 6 and the sealing chamber 8 disappears. The upper valve body 6 moves upward under the rebound force of the upper spring 4, and the lower valve body 9 moves upward under the rebound force of the lower spring 10. The lower valve body 9 moves upward to drive the sealing head 11 upward, and the sealing head 11 moves upward. The production channel 202 below the sealing head 11 is connected with the heat injection channel 201 through the channel connection window 207. At this time, the production channel 202 is opened and can be used for mining, such as Figure 5 As shown, the lower interface 206 of the production channel is connected to the large oil pipe or electric pump required for exploitation. The oil and gas in the formation enter the production channel from the lower interface 206 of the production channel through the large oil pipe or the electric pump, enter the oil pipe from the upper interface 203 of the heat injection channel after passing through the channel connection window 207, and reach the wellhead from the oil pipe.
[0042] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.
[0043] In addition, the terms "one", "two", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In the description of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.
[0044] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.
Claims
1. A thermal insulation joint for an integrated injection and production column, characterized in that: It comprises an inner tube and an outer tube, wherein a heat insulation layer is provided between the inner tube and the outer tube; A heat injection channel and a production channel are provided in the inner tube, and the heat injection channel and the production channel are connected through a channel connection window; An actuator is provided in the production channel. When the actuator is subjected to an action force, the actuator moves to a lower limit position in the production channel, and the production channel and the heat injection channel are not connected. The actuator is located above the lower limit position under normal conditions, and the production channel and the heat injection channel are connected. The actuator is connected to a control mechanism, and the control mechanism can control the actuator to move to a lower limit position in the production channel; The inner tube at the upper part of the production channel is connected with a valve seat, the valve seat is connected with an upper joint, the control mechanism comprises a core shaft arranged in the upper joint, the lower end of the core shaft is connected with an upper valve body, the upper valve body is sealed and connected with the upper joint, and the upper valve body is connected with a lower valve body; The actuator includes a sealing head, the sealing head is threadedly connected with a lower valve body, the lower valve body is connected to the control mechanism, the lower valve body is sealed and connected to the production channel, a first reaming hole is provided at the production channel connected to the channel connection window, the diameter of the first reaming hole is larger than the diameter of the production channel, the sealing head is located in the first reaming hole, and two reduction steps are formed between the first reaming hole and the production channel, wherein the upper first reduction step is the upper limit position of the sealing head movement, and the lower second reduction step is the lower limit position of the sealing head movement; A second expansion hole is opened at the production channel above the first expansion hole, the lower valve body is located in the second expansion hole, and the lower valve body is sealed to the inner wall of the second expansion hole, a reset device 1 is provided in the second expansion hole, and the reset device 1 is connected to the lower valve body.
2. The thermal insulation joint for an integrated injection-production pipe string according to claim 1, characterized in that: The outside of the inner tube is composed of multiple continuous eccentric circles, and two eccentric interfaces are respectively provided at the upper end and the lower end of the inner tube. An upper eccentric interface and a lower eccentric interface are connected to form a heat injection channel, and another upper eccentric interface and another lower eccentric interface are connected to form a production channel.
3. The thermal insulation joint for an injection-production integrated pipe string according to claim 2, characterized in that: The interior of the outer tube is provided with an eccentric circular hole that cooperates with the multiple continuous eccentric circles on the outside of the inner tube. The upper part of the outer tube is provided with two outer tube upper interfaces that cooperate with the eccentric interfaces at the upper end of the inner tube. The outer tube is inserted and matched with the inner tube, and a cable channel is provided on the outer tube.
4. The thermal insulation joint for an injection-production integrated pipe string according to claim 3, characterized in that: The upper joint is connected with a hydraulic pipeline, the control mechanism is arranged in the upper joint, and the control mechanism and the upper joint are sealed and connected.
5. The thermal insulation joint for an injection-production integrated pipe string according to claim 1, characterized in that: The lower end of the first expansion hole is connected to the production channel via the chamfer of the production channel, and the lower part of the sealing head is a conical structure matched with the chamfer of the production channel.
6. The thermal insulation joint for an integrated injection-production pipe string according to claim 1, characterized in that: The first reset device includes a lower spring, which is arranged in the second expansion hole, and the upper end of the lower spring is connected to the lower valve body, and the lower end of the lower spring is connected to the bottom wall of the second expansion hole.
7. The thermal insulation joint for an injection-production integrated pipe string according to claim 1, characterized in that: A second reset device is provided in the upper joint, and the second reset device is connected to the upper valve body; the second reset device includes an upper spring, and the upper spring is sleeved on the core shaft. A positioning cap is fixedly connected in the upper joint, and a hole is provided in the middle of the positioning cap for the core shaft to pass through. The positioning cap is connected to the upper end of the upper spring, and the lower end of the upper spring is connected to the upper valve body.