Multy shield type gate valve

Abstract

The present invention relates to a multi-shield type gate valve, characterized by comprising: a valve body portion having a fluid passage formed therein; a first passage portion installed at one end of the fluid passage; a second passage portion installed at the other end of the fluid passage to communicate with the first passage portion; a driving portion providing opening and closing driving force; a slow pump portion installed to communicate with the fluid passage; a first shield portion installed on the inner circumference of the first passage portion; a second shield portion installed on the inner circumference of the second passage portion; a third shield portion installed on the inner circumference of the first passage portion and positioned below the first shield portion; and a fourth shield portion installed on the inner circumference of the second passage portion and positioned above the second shield portion. Accordingly, the present invention provides the effect of extending the lifespan of a gate valve by preventing corrosion caused by powder in the fluid passage of a valve body part in which the opening and closing part slides, and preventing jamming caused by lumpy powder, thereby reducing sliding failure of the opening and closing part.

Description

Technology Field

[0001] The present invention relates to a multi-shield type gate valve, and more specifically, to a multi-shield type gate valve installed between a vacuum chamber and a vacuum pump to smoothly perform opening and closing operations. Background Technology

[0002] Generally, when performing operations such as etching, deposition, or sputtering processes on LCD (liquid crystal display) substrates or semiconductor wafers, or special coating processes that require a vacuum state like parylene coating, a vacuum environment is created by removing air from inside the chamber where the operation takes place. In this case, it is important to set and maintain an appropriate vacuum level, and a vacuum gate valve is essential for this purpose.

[0003] A vacuum gate valve is located in the passage connecting the chamber and the pump and serves to maintain or release the vacuum state by opening and closing the passage. Typically, such a vacuum gate valve maintains the airtightness of the chamber by sealing the passage leading to the chamber through the operation of a single actuating plate and a single sealing plate.

[0004] Therefore, the sealing technology between the vacuum working area of ​​a semiconductor manufacturing device and the atmosphere also has a significant impact on the quality of semiconductor products. Consequently, a vacuum valve installed between the chamber where the semiconductor device integration process takes place and the vacuum pump that sucks air into the chamber plays an important role in opening and closing the transmission of the vacuum pump's suction force to the chamber, and thus efforts to maintain its lifespan are also emerging as a critical issue.

[0005] In particular, the fluid inside the vacuum chamber discharged through the vacuum gate valve contains various by-products. These by-products are continuously attached to the links of the actuator used to drive the opening and closing plate of the gate valve or to the inner walls of the housing where the opening and closing plate slides when the fluid is discharged, thereby hindering the forward and backward movement of the opening and closing plate and reducing the sealing force between the opening and closing plate and the fluid passage. Therefore, a by-product removal member was required to remove the by-products attached inside the vacuum gate valve.

[0006] Conventional byproduct removal members are equipped with a cleaning gas supply unit installed in the fluid passage of a gate valve to remove foreign substances, such as powder attached to the inside of the body of a vacuum gate valve, by supplying a cleaning gas such as nitrogen.

[0007] However, since this cleaning gas supply unit is additionally installed on the vacuum gate valve and operates depending on whether the vacuum gate valve is open or closed, its structure and control were complex.

[0008] In addition, there was a problem that the cost of removing by-products was high because cleaning gas had to be supplied regularly to continuously remove by-products inside the vacuum gate valve. Furthermore, by-products attached inside the vacuum gate valve could not escape to the outlet by the supplied cleaning gas and moved into the deeper internal space of the vacuum gate valve.

[0009] This not only caused sliding failures of the opening and closing plate, but also had the problem of requiring the entire vacuum gate valve to be disassembled and cleaned, and due to the deterioration of the opening and closing performance and sealing performance of the fluid passage, it also caused processing failures in the processing process of the vacuum semiconductor equipment connected thereto. Prior art literature

[0010] Republic of Korea Published Patent No. 10-2016-0131564 (November 16, 2016) Republic of Korea Registered Patent No. 10-1651251 (August 26, 2016) Republic of Korea Registered Patent No. 10-2202570 (January 13, 2021) The problem to be solved

[0011] The present invention has been devised to resolve the aforementioned conventional problems, and aims to provide a multi-shield type gate valve capable of reducing sliding failures of the opening and closing part by preventing corrosion caused by powder in the fluid passage of the valve body part, in which the opening and closing part slides, and preventing jamming caused by lumpy powder.

[0012] In addition, another objective of the present invention is to provide a multi-shield type gate valve that facilitates installation in a fluid passage by providing a shield piece, a shield groove, a shield jaw, and a shield projection as a shield part, while minimizing contamination caused by the attachment or deposition of products or particulates on the surface by having a low surface friction coefficient of the shield surface.

[0013] In addition, another objective of the present invention is to provide a multi-shield type gate valve capable of reducing the adhesion or deposition of powder in the fluid passage and simultaneously improving the maintenance performance of the fluid passage of the valve body by installing a first shield part, a second shield part, a third shield part, and a fourth shield part made of synthetic resin material in a spaced manner so as to be detachably attached to the fluid passage of the valve body part. means of solving the problem

[0014] The present invention for achieving the above-mentioned purpose comprises: a valve body portion (10) having a fluid passage formed therein; a first passage portion (20) installed on one side of the fluid passage of the valve body portion (10); a second passage portion (30) installed on the other side of the fluid passage of the valve body portion (10) to communicate with the first passage portion (20); a driving portion (40) installed at one end of the valve body portion (10) to provide an opening / closing driving force to open / close the communication portion between the first passage portion (20) and the second passage portion (30); a slow pump portion (50) installed on one side of the valve body portion (10) to communicate with the fluid passage; a first shield portion (60) installed on the inner circumference of the first passage portion (20); and a second shield portion (70) installed on the inner circumference of the second passage portion (30). It is characterized by including: a third shield part (80) installed on the inner circumference of the first passage part (20) and installed at the lower part of the first shield part (60); and a fourth shield part (90) installed on the inner circumference of the second passage part (30) and installed at the upper part of the second shield part (70).

[0015] The third shield portion (80) of the present invention is characterized by comprising: a third shield piece installed on the inner circumference of the first passage portion (20); a third shield projection formed on the circumference of one end of the third shield piece; a third shield projection formed on the circumference of the other end of the third shield piece; a third installation hole formed through one end of the third shield piece; and a third shield groove formed recessed on the inner circumference of the third shield piece.

[0016] The third shield piece of the present invention is characterized by being composed of a shield member made of synthetic resin material installed around the inner circumference of the first passage section (20).

[0017] The fourth shield portion (90) of the present invention is characterized by comprising: a fourth shield piece installed on the inner circumference of the second passage portion (30); a fourth shield projection formed on the circumference of one end of the fourth shield piece; and a fourth shield projection formed on the circumference of the other end of the fourth shield piece.

[0018] The fourth shield piece of the present invention is characterized by being composed of a shield member made of synthetic resin material installed around the inner circumference of the second passage section (30). Effects of the invention

[0019] As described above, the present invention provides the effect of extending the lifespan of a gate valve by preventing corrosion caused by powder in the fluid passage of a valve body part in which the opening and closing part slides, and preventing jamming caused by lumpy powder, thereby reducing sliding failure of the opening and closing part.

[0020] In addition, by providing a shield piece, a shield groove, a shield jaw, and a shield protrusion as a shield part, it facilitates installation in a fluid passage while simultaneously providing the effect of minimizing contamination caused by the attachment or deposition of products or particulates on the surface due to the low surface friction coefficient of the shield surface.

[0021] In addition, by installing a first, second, third, and fourth shield section made of synthetic resin material in a spaced manner so that it can be detachably attached to the fluid passage of the valve body, the effect of reducing the attachment or deposition of powder on the fluid passage and simultaneously improving the maintenance performance of the fluid passage of the valve body is provided. Brief explanation of the drawing

[0022] FIG. 1 is a schematic diagram showing a multi-shield type gate valve according to one embodiment of the present invention. FIG. 2 is a front view showing a multi-shield type gate valve according to one embodiment of the present invention. FIG. 3 is an exploded perspective view showing a multi-shield type gate valve according to one embodiment of the present invention. FIG. 4 is an exploded view showing a multi-shield type gate valve according to one embodiment of the present invention. FIG. 5 is a cross-sectional view showing a multi-shield type gate valve according to one embodiment of the present invention. FIG. 6 is a detailed cross-sectional view showing a multi-shield type gate valve according to an embodiment of the present invention. FIG. 7 is a detailed diagram showing a multi-shield type gate valve according to an embodiment of the present invention. Specific details for implementing the invention

[0023] Hereinafter, a preferred embodiment of the present invention will be described in more detail with reference to the attached drawings.

[0024] FIG. 1 is a configuration diagram showing a multi-shield type gate valve according to an embodiment of the present invention, FIG. 2 is a front view showing a multi-shield type gate valve according to an embodiment of the present invention, FIG. 3 is an exploded perspective view showing a multi-shield type gate valve according to an embodiment of the present invention, FIG. 4 is an exploded view showing a multi-shield type gate valve according to an embodiment of the present invention, FIG. 5 is a cross-sectional configuration diagram showing a multi-shield type gate valve according to an embodiment of the present invention, FIG. 6 is a cross-sectional detailed view showing a multi-shield type gate valve according to an embodiment of the present invention, and FIG. 7 is a detailed view showing a multi-shield type gate valve according to an embodiment of the present invention.

[0025] As shown in FIGS. 1 to 4, the tension-type gate valve according to the present embodiment comprises a valve body part (10), a first passage part (20), a second passage part (30), a driving part (40), a slow pump part (50), a first shield part (60), a second shield part (70), a third shield part (80), and a fourth shield part (90), and is a tension-type gate valve installed between a vacuum chamber and a vacuum pump to smoothly perform opening and closing operations.

[0026] The valve body (10) is a body member having a fluid passage formed therein, and constitutes a vacuum gate valve installed between a vacuum chamber and a vacuum pump. It is formed by including an upper plate, a lower plate, a plurality of side plates, a body flange, and a fixing bracket in a box-shaped body member having a fluid passage formed therein.

[0027] The upper plate forms the upper surface of the valve body (10) and has a through hole formed therein to form a fluid passage, and the lower plate forms the lower surface of the valve body (10) and has a through hole formed therein to form a fluid passage, so that the through holes formed in the upper plate and the lower plate, respectively, form a fluid passage of the valve body (10).

[0028] A sliding space is provided inside the valve body (10), and this sliding space forms a space that slides in a direction perpendicular to the fluid passage so that the opening and closing part opens and closes the fluid passage.

[0029] The first passage section (20) is a passage member installed on one side of the fluid passage of the valve body section (10), and is composed of a tube-shaped passage through which fluid flows in communication with the fluid passage and a first flange formed protrudingly around both ends of the passage to facilitate connection with other members.

[0030] The first flange is connected to the upstream side of the fluid passage to form an upstream communication channel that communicates with the fluid passage, and a flange protruding from the upper circumference of the communication channel is connected to the vacuum chamber, and a flange protruding from the lower circumference of the upstream communication channel is connected to the through hole in the upper plate of the valve body to facilitate connection between the vacuum chamber and the gate valve.

[0031] The second passage section (30) is a passage member installed to communicate with the first passage section (20) at the other end of the fluid passage of the valve body section (10), and is composed of a tube-shaped passage through which fluid flows in communication with the fluid passage, and a second flange formed protrudingly around both ends of the passage to facilitate connection with other members.

[0032] The second flange is connected to the downstream side of the fluid passage to form a downstream communication channel that communicates with the fluid passage, and a flange protruding from the lower circumference of the communication channel is connected to a vacuum pump, and a flange protruding from the lower circumference of the downstream communication channel is connected to the through hole in the lower plate of the valve body to facilitate connection between the vacuum pump and the gate valve.

[0033] In this way, by forming the upstream flange and downstream flange in a tapered shape, either wide or narrow, the powder flowing in through the upstream flange and discharged through the downstream flange passes through the fluid passage at a faster speed than the inlet of the upstream flange. Therefore, it is possible to prevent powder from adhering to the periphery of the fluid passage and the interior of the valve body (10).

[0034] The driving unit (40) is a driving member installed at one end of the valve body (10) to provide opening and closing driving force to open and close the communication portion formed between the first passage portion (20) and the second passage portion (30), and is composed of an actuator and a link mechanism, etc., to slide the opening and closing portion in the forward and backward direction on the outside of one side of the valve body (10).

[0035] The actuator is a driving source that provides sliding driving force to the opening and closing part through a linkage mechanism, and various driving means such as a cylinder or linear motor that provides linear driving force can be used. The actuator can be configured as a separate hydraulic or pneumatic system installed at one end of the valve body (10).

[0036] A linkage mechanism is a power transmission member that converts the linear driving force of an actuator into rotational driving force through a mechanical connection, and slides an opening / closing part in the forward and backward directions by means of that rotational force.

[0037] This link mechanism is located in the sliding space of the valve body (10), and the link mechanism amplifies the linear driving force of the actuator using the lever principle and transmits it as rotational driving force. Therefore, the forward and backward sliding distance of the opening and closing part becomes longer than the linear driving distance of the actuator.

[0038] The slow pump section (50) is a slow pump member installed to communicate with the first passage section (20) and the second passage section (30) on one side of the valve body section (10), and is composed of an opening / closing valve, a first connecting pipe, and a second connecting pipe to form a constant vacuum state upstream and downstream of the gate valve when the fluid passage is opened.

[0039] The shut-off valve is installed between the first connecting pipe connected to the upstream passage and the second connecting pipe connected to the downstream passage, and operates according to the opening and closing of the fluid passage. Additionally, the shut-off valve does not operate when the fluid passage is closed, but operates immediately before the fluid passage opens.

[0040] Accordingly, the operation of the slow pump unit (50) involves injecting air into the interior of the slow pump unit (50) just before the fluid passage is opened to open the shut-off valve, and by opening the shut-off valve, the first and second connecting pipes are connected, thereby connecting the upstream and downstream of the gate valve before the fluid passage is opened to maintain a constant vacuum state.

[0041] That is, when the fluid passage is closed, if the vacuum conditions upstream and downstream of the gate valve are formed differently, there is a high risk of damage to the vacuum pump connected downstream of the gate valve when the fluid passage is opened. Therefore, the slow pump unit (50) is operated before opening the fluid passage to prevent the risk of damage to the vacuum pump.

[0042] The opening / closing part is an opening / closing member installed to slide within the valve body part (10) by a driving part (40) to open / close a communication portion between the first passage part (20) and the second passage part (30), and is composed of an opening / closing plate installed to slide in the sliding space of the valve body part (10) to open / close a fluid passage.

[0043] The opening / closing plate is a plate-shaped member and is installed to intersect vertically with the fluid passage of the valve body (10) and moves back and forth to open and close the inlet of the fluid passage, and a sealing groove is formed on one side of the opening / closing plate in which a sealing member is installed.

[0044] The first shield portion (60) is a shield member that is pressed into one side of the inner circumference of the first passage portion (20) by pressure, and as shown in FIGS. 3 to 7, it comprises a first shield piece, a first slow pump hole (63), a first shield surface (64), a first shield jaw (65), and a first shield projection (66).

[0045] The first shield piece is a shield member that is inserted into the inner circumference of the first passage section (20) and installed by a fastening member such as a bolt, and is composed of a 11th shield piece (61) in the shape of a narrow tube formed so that the diameter becomes narrower as it goes downward, and a 12th shield piece (62) in the shape of a cylinder formed with the same diameter at the top and bottom.

[0046] This first shield piece can be made so as to block foreign substances attached to the inner circumference of the first passage section (20) by inserting a shield member made of synthetic resin material to suppress product deposition and enable smooth shielding operation of the opening and closing section.

[0047] The first slow pump hole (63) is a hole member formed by penetrating a plurality of holes around the circumference of the first shield surface (64), and is connected to the slow pump section (50) to form a constant vacuum state upstream and downstream of the gate valve when the fluid passage is opened.

[0048] The first shield surface (64) is a surface member formed on the inner circumference of the first shield piece, and the first shield surface (64) is made of a synthetic resin material and has a low coefficient of friction on the surface, thereby minimizing contamination caused by the attachment or deposition of products or fine particles (Paticle) on the surface.

[0049] The first shield jaw (65) is a jaw member formed around one end of the first shield piece, and is composed of a spaced-apart joint jaw that is fitted and connected to one end of the first passage section (20) so as to fix the first shield piece at a predetermined distance so as not to contact the inner circumference of the first passage section (20).

[0050] The first shield projection (66) is a projection member formed around the other end of the first shield piece, and is composed of a spaced-apart projection that is fitted and coupled to the other end of the first passage section (20) so as to fix the first shield piece at a predetermined distance so as not to contact the inner circumference of the first passage section (20).

[0051] The second shield portion (70) is a shield member that is pressed into one side of the inner circumference of the second passage portion (30) by pressure, and as shown in FIGS. 3 to 7, it comprises a second shield piece (71), a second slow pump hole (72), a second coupling hole (73), a second shield surface (74), a second shield jaw (75), and a second shield projection (76).

[0052] The second shield member (71) is a shield member installed by being inserted into the inner circumference of the second passage section (30). By inserting a shield member made of synthetic resin material to block foreign substances attached to the inner circumference of the second passage section (30), the deposition of the product is suppressed and the shielding operation of the opening and closing section can be made smooth.

[0053] The second slow pump hole (72) is a hole member formed by penetrating a plurality of holes around the circumference of the second shield surface (74), and is connected to the slow pump section (50) to form a constant vacuum state upstream and downstream of the gate valve when the fluid passage is opened.

[0054] The second coupling hole (73) is a plurality of spaced-apart hole members formed around the protruding portion of the second shield jaw (75), and the second shield piece (71) is coupled by a fastening member such as a bolt in a sliding space where the opening / closing part slides to open / close the fluid passage of the valve body part (10).

[0055] The second shield surface (74) is a surface member formed on the inner circumference of the second shield piece (71), and since the second shield piece (71) is made of a synthetic resin material and has a low coefficient of friction on the surface, the degree of contamination caused by the attachment or deposition of products or fine particles (Paticle) on the surface can be minimized.

[0056] The second shield jaw (75) is a jaw member formed around one end of the second shield piece (71), and is composed of a spaced-apart joint jaw that is fitted and connected to the other end of the second passage section (30) so as to fix the second shield piece (71) at a predetermined distance so as not to contact the inner circumference of the second passage section (30).

[0057] The second shield projection (76) is a projection member formed around the other end of the second shield piece (71), and is composed of a spaced-apart projection that is fitted and coupled to one end of the second passage section (30) so as to fix the second shield piece (71) at a predetermined distance so as not to contact the inner circumference of the second passage section (30).

[0058] The third shield portion (80) is a shield member installed by press-fitting by pressure on the other side of the inner circumference of the first passage portion (20) and installed at the lower part of the first shield portion (60), and as shown in FIGS. 3 to 7, it comprises a third shield piece (81), a third shield jaw (82), a third shield projection (83), a third installation hole (84), and a third shield groove (85).

[0059] The third shield piece (81) is a shield member installed at the lower part of the first shield part (60) and inserted into the inner circumference of the first passage part (20), and is made of a cylindrical shield piece formed with the same diameter at the top and bottom.

[0060] This third shield piece (81) can be configured to block foreign substances attached to the inner circumference of the first passage section (20) by inserting a shield member made of synthetic resin material to suppress product deposition and enable smooth shielding operation of the opening and closing section.

[0061] The third shield jaw (82) is a jaw member formed protruding around one end of the third shield piece (81), and is composed of a spaced-apart joint jaw that is fitted and connected to one end of the first passage section (20) so as to fix-install the third shield piece (81) at a predetermined distance so as not to contact the inner circumference of the first passage section (20).

[0062] The third shield projection (83) is a projection member formed protruding from the circumference of the other end of the third shield piece (81), and is composed of a spaced-apart projection that is fitted and coupled to the other end of the first passage section (20) so as to fix-install the third shield piece (81) at a predetermined distance so as not to contact the inner circumference of the first passage section (20).

[0063] The third installation hole (84) is a plurality of spaced-apart hole members formed around the protruding part of the third shield jaw (82), and the third shield piece (81) is connected by a fastening member such as a bolt in a sliding space where the opening / closing part slides to open / close the fluid passage of the valve body part (10).

[0064] The third shield groove (85) is a groove member formed by being recessed into the inner surface of the third shield piece (81), and it is also possible to support the first shield part (60) and the third shield part (80) by joining them together through the first shield projection (66) in the third shield groove (85).

[0065] The fourth shield portion (90) is a shield member installed on the upper part of the second shield portion (70) and is installed by pressing one side of the protection ring on the inner circumference of the second passage portion (30) by pressure, and is formed by including a fourth shield piece (91), a fourth shield jaw (92), and a fourth shield projection (93) as shown in FIGS. 3 to 7.

[0066] The fourth shield member (91) is a shield member installed by being inserted into the inner circumference of the second passage section (30). By inserting a shield member made of synthetic resin material to block foreign substances attached to the inner circumference of the second passage section (30), the deposition of the product is suppressed and the shielding operation of the opening and closing section can be made smooth.

[0067] The fourth shield jaw (92) is a jaw member formed around one end of the fourth shield piece (91), and is composed of a spaced-apart joint jaw that is fitted and connected to the other end of the second passage section (30) so as to fix the fourth shield piece (91) at a predetermined distance so as not to contact the inner circumference of the second passage section (30).

[0068] The fourth shield projection (93) is a projection member formed around the other end of the fourth shield piece (91), and is composed of a spaced-apart projection that is fitted and coupled to one end of the second passage section (30) so as to fix the fourth shield piece (91) at a predetermined distance so as not to contact the inner circumference of the second passage section (30).

[0069] As described above, according to the present invention, by providing a first shield part, a second shield part, a third shield part, and a fourth shield part in the fluid passage of the valve body part in which the opening / closing part slides, corrosion caused by powder in the fluid passage and the opening / closing part is prevented, and jamming caused by lump powder is prevented, thereby reducing sliding failure of the opening / closing part and providing the effect of extending the lifespan of the gate valve.

[0070] In addition, by providing a shield piece, a shield groove, a shield jaw, and a shield protrusion as a shield part, it facilitates installation in a fluid passage while simultaneously providing the effect of minimizing contamination caused by the attachment or deposition of products or particulates on the surface due to the low surface friction coefficient of the shield surface.

[0071] In addition, by installing a first, second, third, and fourth shield section made of synthetic resin material in a spaced manner so that it can be detachably attached to the fluid passage of the valve body, the effect of reducing the attachment or deposition of powder on the fluid passage and simultaneously improving the maintenance performance of the fluid passage of the valve body is provided.

[0072] The invention described above may be implemented in various other forms without departing from its technical concept or main features. Accordingly, the above embodiments are merely examples in all respects and should not be interpreted restrictively. Explanation of the symbols

[0073] 10: Valve body 20: First passage 30: Second passage section 40: Driving section 50: Slow Pump Section 60: 1st Shield Section 70: 2nd Shield Unit 80: 3rd Shield Unit 90: 4th Shield Unit

Claims

Claim 1 A valve body (10) having a fluid passage formed therein; a first passage section (20) installed on one side of the fluid passage of the valve body (10); a second passage section (30) installed on the other side of the fluid passage of the valve body (10) to communicate with the first passage section (20); a driving section (40) installed at one end of the valve body (10) to provide an opening / closing driving force to open / close the communication portion between the first passage section (20) and the second passage section (30); a slow pump section (50) installed to communicate with the fluid passage of the valve body (10); and a first shield section (60) installed around the inner circumference of the first passage section (20). A second shield portion (70) installed on the inner circumference of the second passage portion (30); a third shield portion (80) including a third shield piece (81) installed on the lower part of the first shield portion (60) and on the inner circumference of the first passage portion (20), a third shield ledge (82) formed on the circumference of one end of the third shield piece (81), a third shield projection (83) formed on the circumference of the other end of the third shield piece (81), a third installation hole (84) formed through one end of the third shield piece (81), and a third shield groove (85) formed indented on the inner circumference of the third shield piece (81); A multi-shield type gate valve comprising: a fourth shield part (90) installed on the inner circumference of the second passage part (30) and installed on the upper portion of the second shield part (70); wherein the first and third shield parts (60, 80) are made of a synthetic resin material and are fixedly installed at a predetermined distance from the inner wall surface of the first passage part (20) by means of a first shield projection (65) protruding from the upper circumference of the first shield part (60) and the third shield projection (82) of the third shield part (80), and are assembled such that a first shield projection (66) formed on the lower circumference of the first shield part (60) and the third shield groove (85) of the third shield part (80) are fitted together to mutually support each other vertically. Claim 2 delete Claim 3 delete Claim 4 A multi-shield type gate valve according to claim 1, wherein the fourth shield portion (90) comprises: a fourth shield piece installed on the inner circumference of the second passage portion (30); a fourth shield projection formed on the circumference of one end of the fourth shield piece; and a fourth shield projection formed on the circumference of the other end of the fourth shield piece. Claim 5 A multi-shield type gate valve according to claim 4, wherein the fourth shield piece is made of a shield member made of synthetic resin material installed on the inner circumference of the second passage section (30).

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