KR102136224B1 - Plasma generator having partition wall - Google Patents

Abstract

The present invention is provided with a plasma generator capable of safely and efficiently generating plasma, and having a plasma generating unit capable of partitioning the interior space at an optimal ratio, and having a plasma generation unit that prevents flow, and stably discharging sludge and scum. It is about.
Plasma generator having a barrier rib structure according to the present invention is formed with a hollow inside, an ozone outlet for discharging ozone is provided on one side at the top, and an outer housing for sludge outlets at which the sludge and scum are discharged are provided on the lower side, and a hollow , A partition wall partitioning each into a production zone on the lower side where plasma is generated, an upper residence zone where ozone generated when plasma is generated, and a discharge zone on the lower side which is a passage through which sludge and scum are discharged, and a part of the outer housing It is characterized in that it is configured to include a plasma generating unit that is installed on the outer side and the other part is installed on the hollow side to generate plasma.

Description

Plasma generator having partition wall structure

The present invention relates to a plasma generator having a structure optimized for the generation of plasma and the discharge of sludge and scum, and more particularly, it is provided with a partition wall capable of dividing the interior space at an optimal ratio, and preventing plasma generation. The present invention relates to a plasma generator capable of safely and efficiently generating plasma, and stably discharging sludge and scum.

In general, plasma is a gas state separated by electrons with negative charges and positively charged ions at very high temperatures, and is called a'fourth material state', and has different physicochemical characteristics depending on the production method, so it has semiconductor, lighting, and display properties. , Medical equipment, environmental improvement business and new energy development, etc.

The apparatus for generating such a plasma has not yet been generalized, so it can be configured and used in various ways depending on the plasma generation method selected by the user, etc. The processing problem is a problem common to most devices for generating plasma, and must be solved to prevent corrosion inside the device and maintain plasma generation efficiency.

The invention of the conventional plasma generating device includes "Plasma Generating Device and Plasma Processing Device" of the Republic of Korea Patent Application Publication No. 2001-0076348 and "Plasma Generating Device and Method" of Korea Patent Publication No. 10-2008-0023061 “Plasma generator” of Korean Patent Publication No. 10-1111207 and “Underwater plasma generator” of Korean Patent Publication No. 10-1476644 have been proposed and published.

The Republic of Korea Patent Application Publication No. 2001-0076348 "plasma generating device and plasma processing device" is configured to change the microwave wavelength in the radiation waveguide by locally changing the dimensions of the radiation waveguide near the slot antenna, thereby Accordingly, an invention has been proposed for a device capable of controlling the intensity distribution of electron radiation emitted from a slot antenna toward a discharge chamber, and the chamber of “Plasma Generating Device and Method” of Korean Patent Publication No. 10-2008-0023061 A lower electrode portion located in the semiconductor substrate, an upper electrode portion facing the lower electrode portion and forming a first plasma source portion, and a second plasma source portion provided at a higher position than the upper electrode portion; An invention has been proposed for a device capable of generating high-density plasma in a low-pressure state by supplying high-temperature electrons to a low-temperature state by being configured to include a power supply for supplying power to the first and second plasma source parts.

In addition, in the “Plasma Generator” of Korean Patent Publication No. 10-1111207, a negative electrode to which a high voltage is applied is provided with a negative electrode assembly provided below and a plasma generating space, but a plurality of plasma generating gases are injected into the space. An invention relating to an apparatus capable of generating plasma efficiently and stably by being configured to include an anode assembly provided with a plasma generating gas injection path and a magnetic generating means for generating magnetic force has been proposed, and the Republic of Korea Patent Publication No. 10-1476644 The “underwater plasma generator” of the heading includes a discharge dielectric tube installed on the upper part of the water tank, a conductive counter electrode installed in the water outside the dielectric tube, and a power supply device for applying power to the conductive counter electrode. Thus, an invention has been proposed for a device capable of generating stable plasma and preventing arcing plasma generation due to a deflected position.

However, the above-mentioned conventional inventions do not clearly present problems related to the use or treatment of ozone generated during plasma generation or the treatment of sludge and scum, and refer to the short circuit problem that may occur when voltage is applied. Since there is no one, there is a need for an invention relating to an apparatus capable of solving such a problem.

Republic of Korea Patent Publication No. 2001-0076348 (2001. 08. 11) Republic of Korea Patent Publication No. 10-2008-0023061 (2008. 03. 12) Republic of Korea Registered Patent Publication No. 10-1111207 (2012. 01. 25) Republic of Korea Registered Patent Publication No. 10-1476644 (2014. 12. 19)

Plasma generator having a partition structure according to the present invention,

When the area of the region where the plasma is generated is narrow compared to the area of the space where ozone generated during the generation of the plasma is generated, a problem in that the efficiency of plasma generation is reduced occurs.

When the area of the zone where the plasma is generated is excessive compared to the area of the space where the ozone generated during the generation of the plasma is generated, there is a problem that the discharge efficiency of the sludge and scum decreases as the atmospheric pressure caused by the excessive ozone increases. ,

When a flow occurs in a device for introducing air and voltage for generating plasma, the purpose of the present invention is to present a solution to this, since internal ozone may flow out and short circuits may occur.

Plasma generator having a partition structure according to the present invention to achieve the above object,

An outer housing in which a hollow is formed inside, an ozone outlet for discharging ozone is provided on one side at the top, and a sludge outlet for discharging sludge and scum is provided at one side at the bottom; A partition wall for partitioning the hollow into a production region on one side of the lower side where plasma is generated, an upper residence region on which ozone generated when plasma is generated, and a discharge region on the lower other side which is a passage through which sludge and scum are discharged; A plasma generating part which is installed on the outer side of the outer housing and the other is installed on the hollow side to generate plasma; It provides a plasma generator having a partition structure, characterized in that comprises a, the partition wall is installed in the hollow, partitioning the area of the production zone and the discharge zone in a ratio of 8: 2, the hollow Characterized in that the length is formed in a ratio of 10:6 to the height.

Plasma generator having a partition structure according to the present invention,

A partition having a length of 5:3 with respect to the height of the hollow is installed so that the area of the production zone and the discharge zone is partitioned at a ratio of 4:1, so that the structure inside the plasma generator is generated by plasma and sludge. And an effect that can be optimized for the discharge of the scum,

By providing a plasma generating portion having a screw-coupled structure to prevent flow, an effect of preventing the outflow and short circuit of ozone occurred.

1 is a cross-sectional view showing the structure of a plasma generator having a partition structure according to the present invention.
Figure 2 is an exemplary view showing an example of use of a plasma generator having a partition structure according to the present invention.
3 is an exemplary view showing a state in which ozone, sludge, and scum are additionally generated when plasma is generated by the plasma generator having the barrier rib structure according to the present invention.
Figure 4 is a cross-sectional view showing the internal structure of the plasma generator of the plasma generator having a partition structure according to the present invention.
5 is an exploded view of a part of the plasma generator of the plasma generator having the barrier rib structure according to the present invention.

First of all, it is revealed that the present invention is a result of the research conducted by the 2017 Small and Medium Business Cooperation Technology Development Project (No.C0503385).

The present invention relates to a plasma generator having a structure optimized for the generation of plasma and the discharge of sludge and scum,

An outer housing 100 in which a hollow 101 is formed inside, an ozone outlet 102 through which ozone is discharged is provided on one side of the upper end, and a sludge outlet 103 through which sludge and scum are discharged is provided on the lower side; The hollow 101, the production zone 111 on the lower side where plasma is generated, the upper residence zone 112 where ozone generated when plasma is generated, and the discharge zone on the lower other side which is a passage through which sludge and scum are discharged. Partition walls 110 partitioned by 113; Plasma generator 200 is installed on the outer side of the outer housing 100, the other part is installed on the hollow 101 side to generate plasma; It relates to a plasma generator having a partition structure, characterized in that comprises a.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, as shown in FIG. 1, a plasma generator having a partition structure according to the present invention has a hollow 101 formed therein, and an ozone outlet 102 through which ozone is discharged is provided on one side of the top, sludge and scum It characterized in that the discharged sludge outlet 103 is configured to include an outer housing 100 provided on one side of the bottom.

The outer housing 100 constitutes the body of the plasma generator.

The hollow 101 formed inside the outer housing 100 is a space in which a plasma called a'fourth material state' is generated as a gas state separated into electrons having negative charges and positively charged ions at an extremely high temperature, and the The ozone outlet 102 is an outlet through which ozone, which is additionally generated in the process of generating plasma, is provided at the top of the outer housing 100 in consideration of the property of ozone as a gas, and the sludge outlet 103 is a plasma As an outlet through which sludge and scum generated additionally with ozone are discharged during the production process, it is provided at the bottom of the outer housing 100 in consideration of the properties of sediment sludge and floating scum.

Additionally, as illustrated in FIG. 2, one end of the ozone discharge pipe, which is a passage through which ozone is discharged, is connected to the ozone outlet 102, and the other end of the ozone discharge pipe is connected to an ejector to supply ozone. With the water flowing into the ejector, it enters into the diffuser inside the ejector so that it can be dissolved in the water.

At this time, the ejector performs the function of ozone so that ozone having a density greater than air can be smoothly discharged to the ozone outlet 102 in addition to the function of dissolving ozone in water.

In addition, as shown in Figure 2, the upper end sludge discharge port 103 is connected to one end of the sludge discharge pipe which is a passage through which sludge and scum are discharged, and the other end of the sludge discharge pipe is connected to an ejector different from the ejector. By supplying sludge and scum, the sludge and scum can be dissolved in water by entering the inside of a diffuser different from the diffuser together with the water flowing into the ejector.However, the treatment of ozone as described above and the sludge and scum The processing is not necessarily limited to this example.

In addition, the ozone outlet 102 is provided above the discharge zone 113 of the following production zone 111 and the following discharge zone 113 for dividing the lower portion of the hollow 101 for smooth discharge of ozone. Preferably, the sludge outlet 103 is provided below the discharge zone 113 so that sludge and scum that have passed through the discharge zone 113 can be discharged to the outside of the outer housing 100.

That is, the following generation zone 111 is a space in which plasma is generated, and the ozone first generated by ozone continuously generated when plasma is generated is pushed out, so that the ozone outlet 102 is located above the generation zone 111. When the ozone is pushed to the upper side of the following discharge zone 113 is not discharged to the outside is more likely to stay for a long time.

For the above reasons, the ozone outlet 102 is preferably provided above the following discharge zone 113, and as shown in FIG. 3, sludge and scum that are additionally generated when plasma is generated are generated zone 111. It is apparent that the sludge discharge port 103 should be provided below the discharge zone 113 because it is passed from to the below discharge zone 113.

In addition, as shown in Figure 1, the plasma generator having a partition structure according to the present invention, the hollow 101, the production zone 111 on the lower side where the plasma is generated, ozone generated during plasma generation is retained It is characterized in that it comprises a partition wall 110 for partitioning into the upper retention zone 112 and the discharge zone 113 on the other side of the lower side which is a passage through which sludge and scum are discharged.

The partition wall 110 divides the hollow 101 inside the plasma generator into three zones, and determines the area ratio between each zone to optimize the plasma generation efficiency and the discharge efficiency of sludge and scum.

That is, when the area of the production zone 111 in which plasma is generated is narrowly formed compared to the area of the residence zone 112 in which ozone generated when plasma is generated resides, additionally generated in the process of plasma generation Since the area of the residence zone 112 is rather large compared to the amount of ozone, this means that the plasma generation efficiency of the plasma generator has not been optimized.

In addition, when the area of the production zone 111 in which plasma is generated is excessively formed compared to the area of the residence zone 112 in which ozone generated during plasma generation resides, an increase in air pressure due to excessive ozone is generated. Accordingly, since the sludge and scum become difficult to pass over the partition wall 110, this means that the discharge efficiency of the sludge and scum of the plasma generator has not been optimized.

That is, the area of the production zone 111 should be configured to have a larger area than the area of the residence zone 112, but the range of the difference between the two areas should be limited, and the discharge zone 113 is based on the plasma production rate. The proportion of the area to the production zone 111 should be determined in consideration of the resulting sludge and scum generation and discharge rates.

Therefore, in order to optimize the plasma generation efficiency of the plasma generator and the discharge efficiency of sludge and scum, the partition wall 110 divides the areas of the generation zone 111 and the discharge zone 113 in a ratio of 4:1. To be installed in the lower portion of the hollow 101, wherein the length of the partition wall 110 is characterized in that it consists of a ratio of 5: 3 with respect to the height of the hollow 101.

Table 1 below configures the ratio of each of the generation zone 111, the residence zone 112, and the discharge zone 113 determined according to the length and installation location of the partition 110, and the sludge outlet Table 103 shows the result of measuring the time for the foam containing sludge and scum to accumulate to 80% of the height of the partition 110 when closed (103).

At this time, when the sludge outlet 103 is opened, it is revealed that the bubbles did not accumulate to 80% of the height of the partition wall 110 under any conditions described in the table below, that is, the discharge of the foam to the outside proceeded smoothly.

Creation zone Discharge area Residence zone Time(t) 4 One 5 30 3 One 4 27 4 One 4 22 5 2 3 18 4 One 3 15

Therefore, as described in Table 1, the internal ratio of the hollow 101 partitioned by the partition wall 110 is the production zone 111, the discharge zone 113 and the residence zone 112, respectively. It can be seen that sludge and scum can be efficiently discharged while minimizing the ratio of the discharge zone 113 to the production zone 111 when formed at a ratio of 4:1:3.

In addition, the partition wall 110 may be formed vertically at an angle of 90° from the bottom of the plasma generator or be inclined at an angle of 1 to 30° toward the discharge area to improve the discharge speed of sludge and scum. It is characterized in that, even when it is formed to be inclined at an angle of 1 to 30° toward the discharge zone, the proportion of each zone must be kept constant, so the position where the partition 110 is installed varies depending on the slope of the partition 110 Should be constructed.

However, when the inclination of the partition 110 is formed in a range of 1 to 5°, the effect of improving the discharge speed of sludge and scum according to the inclination of the partition 110 may be weak, and the inclination of the partition 110 When formed at 31° or more, the entry path to the discharge zone 113 is narrowed, and thus a bottleneck phenomenon in which the discharge speed of sludge and scum is limited may occur, so the slope of the partition wall 110 is within a range of 6 to 30° It is preferably formed, but is not necessarily limited thereto.

In addition, as shown in Figure 1, a plasma generator having a partition structure according to the present invention is a part is installed on the outer side of the outer housing 100, the other part is installed on the side of the hollow 101 plasma It characterized in that it comprises a plasma generating unit 200 to generate.

The plasma generating unit 200 is configured to allow air to flow into the inside of the plasma generator, is configured to receive a voltage from the outside, and discharges by applying voltage and contacting air to generate plasma. By providing 240, plasma is generated in the generation zone 111.

Specifically, as shown in FIGS. 4 and 5, the plasma generating unit 200 is provided with a horizontal tube 212 on which a horizontal first passage 211 is formed, and is provided vertically therein. The vertical passage 214 in which the third passage 213 is formed is provided at the bottom, and the second passage 215 having an'a' shape communicating with the first passage 211 and the third passage 213 is provided. It is formed in the interior, it characterized in that it comprises a head portion 201 is provided with an application unit 216 is applied with a voltage on the upper end.

The first passage 211 is an entry path through which air enters the interior of the head portion 201, and the third passage 213 is an entry path through which air enters the outside of the head portion 201. 2 passage 215 converts the direction of the air that has entered the first passage 211 to the right angle direction.

At this time, the upper end of the head unit 201 is provided with an application unit 216 to which a voltage is applied, so the voltage applied to the application unit 216 is configured to supply current to the discharge unit 240 below, so that the application unit ( The material of the head portion 201 except 216) is preferably made of ceramic or the like having excellent insulating properties, and thus it is preferable to prevent an electric leakage.

In addition, as shown in Figures 4 and 5, the plasma generation unit 200 is characterized in that it comprises a discharge tube 220 through which the fourth passage 221 passing through the top and bottom is formed therein The air that has advanced from the head portion 201 flows along the fourth passage 221 and continuously contacts the discharge portion 240 to generate discharge.

At this time, the discharge tube 220, it is preferable that the length is sufficiently extended downward so that the generation of the plasma by the following discharge unit 240 can be performed in the generation zone 111, the material is most preferably a quartz tube However, it may be composed of a ceramic tube or a glass tube.

In addition, as shown in FIGS. 4 and 5, the plasma generating unit 200 is formed with a first insertion path 231 into which a lower portion of the vertical tube 214 is inserted, and the discharge tube. A second insertion path 232 into which the upper part of the 220 is inserted is formed on the lower side of the interior, and a communication path 233 communicating the first insertion path 231 and the second insertion path 232 is provided. Characterized in that it comprises a connection portion 230 formed in the middle.

The connection part 230 is provided on the upper side of the outer housing 100 in a form in which a part is located outside the outer housing 100 and the other part is located on the hollow 101 side, the head part 201 ) To be provided on the outside of the outer housing 100, and the discharge tube 220 and the discharge portion 240 can be provided on the hollow 101 side.

When the head unit 201 and the discharge tube 220 are directly connected, any one or more of the two may be damaged due to accumulation of vibration generated when plasma is generated, so the connection unit 230 is connected to the head unit 201 It is preferable that the discharge tube 220 is spaced a predetermined distance to prevent damage such as the above, and thus is composed of an elastic body such as silicone capable of absorbing vibration.

As an embodiment of the present invention, the connecting portion 230 may be composed of an elastomer having excellent chemical resistance, elasticity, and resilience, and accordingly, part of the inserted head portion 201 and part of the discharge tube 220 It is hermetically sealed to prevent the leakage of ozone and electric current, while obtaining an excellent effect on durability.

Silicone rubber is mainly used as the elastomer, but in the present invention, fluorine-based rubber may be used in consideration of pressure caused by ozone.

Preferably, block copolymers of vinylidene fluoride (VDF) and 6-propylene fluoride (HFP) or block copolymers of 4-ethylene fluoride (TFE) and 6-propylene fluoride (HFP) in consideration of properties such as heat resistance and chemical resistance A fluorine-based rubber made of a coalescence may be used. In particular, when forming the copolymer, 6-fluorinated propylene (HFP) has 6 fluorine atoms in the molecule, so the content of fluorine is high. In order to form a polymer, it is preferable that in the case of a block copolymer of vinylidene fluoride (VDF) and 6-propylene fluoride (HFP), it is preferable to polymerize to a molar ratio of 1:3 or 1:4, and 4-ethylene fluoride In the case of a block copolymer of (TFE) and 6-propylene fluoride (HFP), since the fluorine content of 4-ethylene fluoride (TFE) is higher than that of vinylidene fluoride (VDF), polymerization is performed at a molar ratio of 1:2 or 1:3. It is preferred.

In addition, 10 to 20 parts by weight of carbon black, 1 to 3 parts by weight of a reinforcing agent such as calcium hydroxide, and 1 to 3 parts by weight of an oxidizing agent such as calcium oxide or potassium oxide to improve electrical properties and durability It is preferable to use a rubber composition composed of 0.1 to 1 part by weight of a vulcanizing agent such as a part, a chlorine-based vulcanizing agent, or a bisphenol-based vulcanizing agent.

In addition, as shown in Figures 4 and 5, the plasma generator having a partition structure according to the present invention is formed with a thread 217 on a part of the outer side of the vertical tube 214, the connection portion 230 It characterized in that the screw groove 234 corresponding to the thread 217 is formed on the inner side, the vertical pipe 214 by the above configuration is securely fastened to the connection portion 230 to prevent flow , It is a configuration that prevents the outflow of ozone into the gaps of the components constituting the plasma generating unit 200 and also prevents short circuits due to current leakage to the outside of the plasma generating unit 200.

That is, since the inside of the plasma generator is in a high humidity for reasons due to the following bubble generator 250 or the like, if the head part 210 and the connection part 230 are fastened only by a simple insertion method, the head part 210 is lifted. As the descent is facilitated, ozone may flow out to the outside and a short circuit may occur, so that the threads 217 and the screw grooves 234 combine the head portion 210 and the connection portion 230. Robustness prevents the occurrence of the above problems.

In addition, the horizontal tube 212 may be connected to a horizontal pipe (not shown) having a sub-path (not shown) having a diameter smaller than the diameter of the first passage 211, the horizontal pipe is the hollow ( 101) It can be used for the purpose of controlling the amount of plasma generated by controlling the amount of air flowing into the interior. Accordingly, the size of the sub-path may be formed of a plurality of individuals.

In addition, as shown in FIGS. 4 and 5, the plasma generating part 200 includes a discharge part 240 in which a part is inserted into the vertical tube 214 and another part is inserted into the discharge tube 220. It characterized in that the configuration, and the discharge unit 240 generates a plasma by contacting and discharging the air flowing along the fourth passage 221 in a state in which a current is supplied from the application unit 216.

In addition, as shown in Figures 4 and 5, the plasma generation unit 200 is characterized in that it comprises a bubble generator 250 connected to the lower portion of the discharge tube 220, the bubble generation The foam generated by the unit 250 fills the interior of the production zone 111 and rises, then passes to the discharge zone 113 so that sludge and scum contained in the foam can be discharged outside the plasma generator.

The embodiments introduced above are provided as examples to ensure that the technical spirit of the present invention can be sufficiently transmitted to a person having ordinary knowledge in the technical field to which the present invention pertains, and the present invention is directed to the embodiments described above. It is not limited and may be embodied in other forms.

In order to clearly describe the present invention, parts irrelevant to the description are omitted in the drawings, and in the drawings, the width, length, and thickness of components may be exaggerated or reduced for convenience.

In addition, the same reference numbers throughout the specification indicate the same components.

100: outer housing
101: hollow 102: ozone outlet
103: sludge outlet
110: bulkhead
111: production zone 112: residence zone
113: discharge area
200: plasma generator
210: head
211: first passage 212: horizontal tube
213: third passage 214: vertical tube
215: second passage 216: authorization unit
217: thread
220: discharge tube
221: passage 4
230: connection
231: 1st insertion path 232: 2nd insertion path
233: communication path 234: screw groove
240: discharge unit
250: bubble generator

Claims (5)

An outer housing 100 in which a hollow 101 is formed, an ozone outlet 102 through which ozone is discharged is provided on one side of the upper end, and a sludge outlet 103 through which sludge and scum are discharged is provided on one side of the bottom;
The hollow 101, a production zone 111 on the lower side where plasma is generated, an upper residence zone 112 where ozone generated during plasma generation stays, and a discharge zone on the lower other side which is a passage through which sludge and scum are discharged. Partition walls 110 partitioned by 113;
A plasma generating unit 200 which is installed on the outer side of the outer housing 100 and the other is installed on the hollow 101 side to generate plasma; Consisting of, including
The plasma generating unit 200,
It is configured to include a discharge portion 240, a part of which is inserted into the vertical tube 214 and the other part of which is inserted into the discharge tube 220,
It is configured to include a bubble generator 250 connected to the lower portion of the discharge tube 220, the bubbles generated by the bubble generator 250 fills the interior of the production zone 111, and then rises to the discharge zone ( 113) so that the sludge and scum contained in the foam can be discharged to the outside.
In the ozone outlet 102,
One end portion of the ozone discharge pipe is connected, and the other end portion of the ozone discharge pipe is connected to an ejector to form a partition structure characterized in that ozone enters into the diffuser inside the ejector together with the water flowing into the ejector and dissolves in the water. Eggplant plasma generator.
According to claim 1,
The partition wall 110,
It is installed in the hollow 101,
The area of the production zone 111 and the discharge zone 113 is divided into a ratio of 8:2,
Plasma generator having a partition structure, characterized in that the length is formed in a ratio of 10:6 with respect to the height of the hollow (101).
According to claim 1,
The partition wall 110,
Plasma generator having a partition structure, characterized in that a slope of 1 to 30 ° is formed toward the discharge zone (113).
According to claim 1,
The plasma generation unit 200,
A horizontal tube 212 in which a horizontal first passage 211 is formed is provided on the side, and a vertical tube 214 in which a vertical third passage 213 is formed is provided at the bottom, and the agent is The first passage 211 and the second passage 215 having an'A' shape communicating with the third passage 213 are formed therein, and a head portion provided with an application portion 216 to which a voltage is applied at the top ( 201);
A discharge tube 220 through which a fourth passage 221 penetrating the upper and lower ends is formed;
A first insertion path 231 into which the lower part of the vertical tube 214 is inserted is formed on the inside, and a second insertion path 232 into which the upper portion of the discharge tube 220 is inserted is on the lower side inside. It is formed, the first insertion path 231 and the communication path 233 communicating the second insertion path 232 is formed in the middle of the connection portion 230; Plasma generator having a partition structure, characterized in that comprises a.
According to claim 4,
A thread 217 is formed on a part of the outer side middle end of the vertical tube 214,
A plasma generator having a partition structure, characterized in that a thread groove 234 corresponding to the thread 217 is formed on the inner side of the connection part 230.

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