JP2009121512A - On-off valve for powder flow passage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an on-off valve for a powder flow passage capable of preventing any catch of powder in a substantially complete manner when closing a valve element. <P>SOLUTION: In the on-off valve for the powder flow passage, a circular valve element 14 for opening/closing its flow passage is built in a powder flow passage 13 formed inside a cylindrical valve body 11, and an outer circumferential part of the valve element 14 is brought into contact with a seat ring 12 provided along an inner circumferential surface of the flow passage of the valve body 11 by the turn of the valve element 14 to close the flow passage 13. The valve element 14 has an air feed hole 18 extending in the radial direction and opened at an end face of a valve stem, and a plurality of air jet holes 19 extending radially from a center of the valve element 14 and communicated with the air feed hole. Compressed air is fed to the air feed hole 18 when closing the valve element 14, the compressed air is jetted outwardly in the radial direction of the valve element 14 from the air jet holes 19, and powder is blown with the jet air to prevent the powder from being caught by an abutted part of the valve element 14 and the seat ring 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an on-off valve that opens and closes a powder flow passage.

  In a classification plant that centrifuges powder into coarse powder and fine powder, and uses the fine powder as a product, a hopper for supplying powder is connected to the first air classifier for primary classification, and the first air stream classification from the hopper. The powder supplied into the classification chamber of the machine is swirled at high speed and centrifuged into coarse powder and intermediate powder (fine powder containing coarse powder), and the intermediate powder is classified into the classification chamber of the second air classifier for secondary classification The product is rotated at high speed in the classification chamber, centrifuged into coarse powder and fine powder, and the fine powder sucked into the fine powder discharge cylinder is guided to a solid-gas separator such as a cyclone separator to collect the fine powder that becomes the product I am trying to process it.

  In the above classification plant, the powder supply flow path connecting the powder supply hopper and the first airflow classifier, or the flow for intermediate powder flow connecting the first airflow classifier and the second airflow classifier. An on-off valve is incorporated in the passage, and the flow of the powder is controlled by opening and closing the passage with the on-off valve.

  Here, since the flow path of the powder containing fine powder has a relatively large diameter, a circular valve body is incorporated in the flow path formed in the valve body as an on-off valve, and the flow path is formed by turning the valve body. A butterfly valve that opens and closes and a slide valve that opens and closes the flow path by sliding a valve plate in a direction crossing the flow path formed in the valve body are generally used.

  By the way, in the butterfly valve described above, when the valve body is in a closed state, the powder is caught in the contact portion between the seat ring and the valve body provided along the inner periphery of the flow path of the valve body. There is a disadvantage that the powder particles are flattened or the powder particles are bonded together to form a lump.

  Also in the slide valve, when the valve plate is in a closed state, the powder is caught in the contact portion between the seal member and the valve plate provided on the inner periphery of the flow path of the valve body. There is a disadvantage that the powder particles are flattened or the powder particles are bonded together to form a lump.

In order to eliminate the above inconvenience, in Patent Document 1, the thickness of the valve body is gradually reduced as it is moved away from the valve shaft, and the thickness at the portion orthogonal to the rotation axis of the valve shaft is reduced to be the smallest. We have proposed a butterfly valve designed to prevent intrusion.
JP 2004-190820 A

  By the way, in the above-mentioned conventional butterfly valve, since the thickness at the portion orthogonal to the rotation axis of the valve shaft is the thinnest, biting at that portion can be almost completely prevented, but at the portion where the thickness is thick There is a problem that biting cannot be prevented.

  An object of the present invention is to provide an on-off valve for a powder flow path, which can prevent powder biting almost completely.

  In order to solve the above-mentioned problems, in the first invention, a circular valve body for opening and closing the flow path is incorporated in a powder flow path formed inside a cylindrical valve body, and the valve The valve body is rotated by rotating the valve stem provided on the body, and the outer periphery of the valve body is brought into contact with the seat ring provided along the inner peripheral surface of the valve body to close the flow path. In the opening / closing valve for the powder flow path, the valve body, the air supply hole extending in the radial direction and opening at the end face of the valve rod, and extending radially from the center of the valve body and communicating with the air supply hole, A configuration in which a plurality of air injection holes for injecting the compressed air supplied to the air supply holes from the outer periphery of the valve body toward the radially outer side is employed.

  In the on-off valve configured as described above, compressed air is supplied to the air supply hole when the open valve body is closed. By supplying the compressed air, the compressed air flows into a plurality of radially arranged air injection holes, and is injected radially outward from the outer periphery of the valve body. The powder adhering to the inner peripheral surface is blown away, and the powder is not caught in the contact portion between the valve body and the seat ring when the valve body is closed.

  Here, the supply of compressed air to the air supply hole may be performed prior to closing the valve body, or may be performed at a position just before the valve body is completely closed. . In some cases, compressed air may be constantly injected.

  In the on-off valve according to the first aspect of the present invention, high-pressure air that communicates with the air injection hole and diverges from the air injection hole is obliquely removed from the outer peripheral portions of both side surfaces of the valve element. If the inclined hole for injecting toward the direction is provided, the compressed air can be injected over a wide range of the outer periphery of the valve body, so that the biting of the powder can be prevented more reliably.

  In order to solve the above-mentioned problems, in the second invention, a circular valve body for opening and closing the flow path is incorporated in the flow path of the powder formed inside the cylindrical valve body, and the valve The valve body is rotated by rotating the valve stem provided on the body, and the outer periphery of the valve body is brought into contact with the seat ring provided along the inner peripheral surface of the valve body to close the flow path. In the opening / closing valve for the powder passage, an annular air chamber is formed between the outer peripheral surface of the seat ring and the inner peripheral surface of the valve body, and the compressed air supplied to the air chamber is supplied to the seat ring This is a configuration in which a plurality of air injection holes for injecting the air from the valve body abutting portion of the seat ring into the flow path are formed at intervals in the circumferential direction.

  In the on-off valve configured as described above, compressed air is supplied to the air chamber, the compressed air is injected from each of the plurality of air injection holes, and the valve body is closed in a state where the powder is blown off by the injection air. To do. Even in this case, the biting of the powder can be prevented.

  In order to solve the above-mentioned problem, in the third invention, a circular flow path for powder flow is formed in the valve body, and the flow path is opened in a part of the outer periphery of the valve body across the radial direction. A seal housing space is provided, and a seal member incorporated in the seal housing space is formed with a circular hole coaxially with the flow path and a valve body insertion hole extending from a part of the outer periphery to the circular hole. The valve plate is slidably inserted into the insertion hole, the valve plate is slid toward the circular hole, and the flow path is closed by bringing the semicircular outer peripheral surface of the tip of the valve plate into close contact with the inner periphery of the circular hole. In the open / close valve for a powder passage, the valve plate has an air supply hole extending in a sliding direction of the valve plate from a rear end surface thereof, and extending radially from the center of curvature of the semicircular outer peripheral surface to the air supply hole. Communicated and supplied to the air supply hole The compressed air is of employing the configuration to form a plurality of air injection holes for injecting radially outward from the semi-circular outer peripheral surface.

  In the on-off valve according to the third aspect of the invention, compressed air is supplied to the air supply hole, and the compressed air is injected from the plurality of radially arranged air injection holes toward the outer periphery of the semicircular outer peripheral surface. The valve plate is closed while the powder is blown away by air to prevent the powder from being caught.

  Furthermore, in order to solve the above-mentioned problems, in the fourth invention, a circular flow path for powder flow is formed in the valve body, and the flow path is opened at a part of the outer periphery of the valve body across the radial direction. A seal housing space is provided, and a seal member incorporated in the seal housing space is formed with a circular hole coaxially with the flow path and a valve body insertion hole extending from a part of the outer periphery to the circular hole. The valve plate is slidably inserted into the insertion hole, the valve plate is slid toward the circular hole, and the flow path is closed by bringing the semicircular outer peripheral surface of the tip of the valve plate into close contact with the inner periphery of the circular hole. In the open / close valve for the powder flow path, a semicircular air chamber is formed between the outer peripheral surface of the circular hole forming portion of the seal member and the inner peripheral surface of the seal storage space. The compressed air supplied to the air chamber is valved. It had adopted a configuration formed at intervals a plurality of air injection holes in a circumferential direction for ejecting toward the semi-circular outer peripheral surface of the over bets.

  In the on-off valve according to the fourth aspect of the present invention, compressed air is supplied to the air chamber, and the compressed air is injected from each of the plurality of air injection holes toward the semicircular outer peripheral surface of the valve plate. The valve plate is closed while the powder is blown away to prevent the powder from being caught.

  In the on-off valve according to the first invention, as described above, the valve body has an air supply hole extending in the radial direction and a plurality of air injection holes extending radially from the center of the valve body and communicating with the air supply hole. And the compressed air supplied to the air supply hole is injected from each of the plurality of air injection holes outward in the radial direction of the valve body. Powder can be blown off by the jet air that is generated, and it is possible to prevent the powder from biting into the contact portion between the valve body and the seat ring when the valve body is closed.

  In the second invention, an annular air chamber is formed between the outer peripheral surface of the seat ring and the inner peripheral surface of the flow path of the valve valve body, and the compressed air supplied to the air chamber is supplied to the seat ring. Since a plurality of air injection holes for injecting into the flow path from the valve contact part of the ring are formed at intervals in the circumferential direction, the powder is injected by the injection air injected from each of the plurality of air injection holes. In the same manner as in the first aspect, the powder can be prevented from biting into the contact portion between the valve body and the seat ring when the valve body is closed.

  Further, in the third invention, the air supply hole extending in the sliding direction of the valve plate, the valve plate, extending radially from the center of curvature of the semicircular outer peripheral surface of the valve plate, and communicating with the air supply hole. By forming a plurality of air injection holes for injecting the compressed air supplied to the supply holes radially outward from the semicircular outer peripheral surface, powder is generated by the injection air injected from each of the plurality of air injection holes. The body can be blown away, and the powder can be prevented from biting into the contact portion between the valve plate and the seal member in the closed state of the valve plate.

  In the fourth aspect of the invention, a semicircular air chamber is formed between the outer peripheral surface of the seal member and the inner peripheral surface of the seal housing space, and the compressed air supplied to the air chamber is supplied to the seal member as a valve plate. Since the plurality of air injection holes for injecting toward the semicircular outer peripheral surface of the plurality of air injection holes are formed at intervals in the circumferential direction, the powder can be blown off by the injection air injected from each of the plurality of air injection holes. Similar to the third aspect of the invention, it is possible to prevent the powder from biting into the contact portion between the valve plate and the seal member in the closed state of the valve plate.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment of an on-off valve according to the present invention. As shown in the figure, an on-off valve 10 according to the present invention is incorporated in a connection portion between the first powder flow cylinder 1 and the second powder flow cylinder 2.

  The on-off valve 10 has a cylindrical valve body 11, and a seat ring 12 made of an elastic material such as rubber is provided on the inner periphery of the valve body 11, and a powder flow path 13 is disposed inside the seat ring 12. It is said that.

  A circular valve body 14 is incorporated in the flow path 13, and a valve rod 15 provided on the valve body 14 penetrates the seat ring 12 and is formed in a valve rod insertion hole 16 formed at a position facing the valve body 11. It is inserted in and is rotatably supported by the valve rod insertion hole 16.

  The valve body 14 is configured to open and close the flow path 13 by rotating around the valve stem 15 by a rotational torque applied to the valve stem 15, and the outer peripheral portion of one side surface of the valve body 14 in the closed state. The outer peripheral portion of the other side facing the outer peripheral portion comes into contact with the seat surface 17 having a circular cross section formed on the inner periphery of the seat ring 12.

  The valve body 14 extends in the radial direction and opens at one end surface of the valve rod 15. The valve body 14 extends radially from the center of the valve body 14 and communicates with the air supply hole 18. A plurality of air injection holes 19 that are open on the outer peripheral surface are formed.

  An air supply cylinder 21 is connected to one end of the valve stem 15 via a swivel joint 20. When compressed air is supplied from the air supply cylinder 21 into the air supply hole 18, the compressed air is supplied to the plurality of air injection holes 19. From each of these, it injects toward the radial direction outward of the valve body 14.

  The on-off valve shown in the first embodiment has the above-described structure, and when the flow path 13 is closed, a rotational torque is applied to the valve rod 15 so that the outer periphery of the valve element 14 is formed on the inner periphery of the seat ring 12. The valve body 14 is rotated to a position where it comes into contact with the seat surface 17 thus made.

  FIG. 3 (II) shows a state in the middle of closing the valve body 14 in the open state, and FIG. 3 (I) shows a state in which the valve body 14 is closed. When the valve body 14 is closed, compressed air is supplied to the air supply cylinder 21.

  Here, when compressed air is supplied to the air supply cylinder 21, the compressed air flows from the air supply hole 18 to the plurality of radially arranged air injection holes 19, and as shown by arrows in FIG. 14 is ejected radially outward from the outer periphery of the nozzle 14, and the powder around the valve element 14 and the powder adhering to the inner periphery of the seat ring 12 are blown off by the spray air. For this reason, when the valve body 14 is closed, the powder does not bite into the contact portion between the valve body 14 and the seat surface 17 of the seat ring 12.

  Here, the supply of compressed air to the air supply cylinder 21 may be performed prior to closing the valve body 14, or may be performed at a position slightly before the valve body 14 is completely closed. May be. In some cases, compressed air may be constantly injected.

  In the on-off valve 10 as described above for preventing the powder from being caught by injecting air from the outer periphery of the valve body 14, as shown in FIGS. 4 (I) and (II), the air injection port of the air injection hole 19 is used. When a pair of inclined holes 22 that are inclined in the opposite direction and communicated with the air injection holes 19 are formed in the part, the compressed air flowing through the air injection holes 19 is divided into the pair of inclined holes 22. Since the air is also injected from each of the pair of inclined holes 22, the compressed air can be injected over a wide range of the outer periphery of the valve body 14, and the biting of the powder is more reliably performed. Can be prevented.

  In the embodiment shown in FIG. 3, the valve body 14 is closed and held in a sealed state by contact with the seat surface 17 formed on the inner periphery of the seat ring 12, but means for maintaining the sealed state is It is not limited to this.

  For example, as shown in FIGS. 5 (I) and (II), an annular protrusion 23 is formed on the inner peripheral surface of the valve body 11, and engagement grooves 24 are formed on the outer peripheral portions of both side surfaces of the annular protrusion 23. Then, flanges 26 are provided at both ends of the outer periphery of the elastically deformable seat ring 25 incorporated inside the annular protrusion 23, and a protrusion 27 that engages with the engagement groove 24 is formed on the flange 26. An annular air reservoir 28 is provided between the inner peripheral surface of the annular protrusion 23 and the outer peripheral surface of the seat ring 25, and compressed air is supplied to the air reservoir 28 from an air supply port 29 formed in the valve body 11. Then, as shown in FIG. 5 (II), a seat ring 25 that is elastically deformed in the inner diameter direction may be brought into close contact with the outer peripheral portion of the valve body 14 to maintain a sealed state.

  6 and 7 show a second embodiment of the on-off valve according to the present invention. In this embodiment, an annular air chamber 30 is formed on the outer peripheral surface of the seat ring 12 fixed to the inner periphery of the valve body 11, and the seat ring 17 communicates with the air chamber 30 to form the seat surface 17. A plurality of air injection holes 31 that are opened in the circumferential direction are provided at intervals in the circumferential direction, compressed air is supplied into the air chamber 30 from an air supply cylinder 32 connected to the valve body 11, and the compressed air is injected into the plurality of air jets. It is made to inject into the flow path 13 from each of the hole 31. FIG.

  The on-off valve shown in this embodiment and the on-off valve shown in the first embodiment are such that the on-off valve shown in the first embodiment injects compressed air toward the outer periphery of the valve body 14. On the other hand, the on-off valve shown in the second embodiment is different in that compressed air is injected from the seat ring 12 side into the flow path 13.

  Since the other structure is the same as that of the on-off valve shown in the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  Also in the on-off valve shown in the second embodiment, the valve element 14 is closed because the compressed air injected from the air injection hole 31 can flow in the flow path 13 or blow off the floating powder. Sometimes it is possible to prevent biting of the powder.

  In the second embodiment, the air chamber 30 is formed on the outer peripheral surface of the seat ring 12, but the air chamber may be formed on the inner peripheral surface of the valve body 11.

  8 and 9 show a third embodiment of the on-off valve according to the present invention. In the on-off valve shown in this embodiment, a valve plate 43 is slidably provided in a direction crossing the flow path 42 with respect to a circular flow path 42 formed in the valve body 41. It comprises a slide valve that opens and closes the flow path 42 by the operation of a cylinder 44 connected to the rear end.

  Here, in the valve body 41, a pair of plate bodies 46 whose outer periphery is the same shape as the outer periphery of the casing 45 are superimposed on the upper and lower surfaces of the U-shaped casing 45, and the upper surface of the upper plate body 46 and the lower plate body 46 are overlapped. Rings 47 are stacked on each of the lower surfaces, and each member is joined and integrated by tightening bolts 48 that are screwed from one ring 47 into the other ring 47. The inner side of each ring 47 is the flow of powder. This is a road 42.

  A space formed between the U-shaped casing 45 and the pair of plate bodies 46 is a seal storage space 50, and the seal storage space 50 is a part of the outer periphery of the casing 45 across the flow path 42 in the radial direction. The seal member 51 is assembled in the seal housing space 50.

  The seal member 51 is formed with a circular hole 52 coaxially with the flow path 42 and a flat valve element insertion hole 53 extending from a part of the outer periphery to the circular hole 52. The width dimension of the valve element insertion hole 53 is as follows. The inner diameter of the circular hole 52 is the same, and the valve plate 43 is slidably inserted into the valve element insertion hole 53.

  The outer periphery of the tip of the valve plate 43 is a semicircular shape along the inner periphery of the circular hole 52, and an air supply hole 54 extending from the rear end surface in the sliding direction of the valve plate 43 and a semicircular outer peripheral surface 55. A plurality of air injection holes 56 that extend radially from the center of curvature and communicate with the air supply hole 54 and inject compressed air supplied to the air supply hole 54 radially outward from the semicircular outer peripheral surface 55. Is formed.

  An air supply cylinder 57 that supplies compressed air to the air supply hole 54 is connected to the rear end of the valve plate 43.

  In the on-off valve configured as described above, when compressed air is supplied from the air supply cylinder 57 to the air supply hole 54, the compressed air flows into the plurality of air injection holes 56, and then from the semicircular outer peripheral surface 55 of the valve plate 43 in the radial direction. Since it injects outward, the powder in the flow path 42 can be blown off by the injection air.

For this reason, when the valve plate 43 is closed, the valve plate 43 is closed in a state in which compressed air is injected from each of the plurality of air injection holes 56, so that the semicircular outer peripheral surface 55 and the circular hole of the valve plate 43 are closed. It is possible to prevent the powder from being caught between the inner peripheral surfaces of 52.

  FIG. 10 shows a fourth embodiment of the on-off valve according to the present invention. In the on-off valve shown in this embodiment, a semicircular air chamber 58 is formed between the semicircular outer peripheral surface at the circular hole forming portion of the seal member 51 and the inner peripheral surface of the seal storage space 50, and the seal member 51. A plurality of air injection holes 59 for injecting compressed air supplied to the air chamber 58 toward the semicircular outer peripheral surface 55 of the valve plate 43 are formed at intervals in the circumferential direction.

  Here, when forming the air chamber 58, a groove extending in the circumferential direction is formed on the semicircular outer peripheral surface of the seal member 51, and the groove is used as the air chamber 58. However, the groove is formed on the semicircular inner peripheral surface of the seal storage space. The groove may be formed as an air chamber.

  The on-off valve shown in the fourth embodiment and the on-off valve shown in the third embodiment are such that the on-off valve shown in the third embodiment opens at the semicircular outer peripheral surface 55 of the valve plate 43. While the compressed air is injected from the injection hole 56, the on-off valve shown in the fourth embodiment causes the compressed air to be injected into the circular hole 52 from the air injection hole 59 formed in the seal member 51. It is different in that it is.

  For this reason, the same code | symbol is attached | subjected to the component same as the on-off valve shown in 3rd Embodiment, and description is abbreviate | omitted.

  Also in the on-off valve shown in the fourth embodiment, the valve plate 43 can be closed because the compressed air injected from the air injection hole 59 can flow in the circular hole 52 or blow off the floating powder. Sometimes, it is possible to prevent the powder from being caught between the semicircular outer peripheral surface 55 of the valve plate 43 and the inner peripheral surface of the circular hole 52.

Longitudinal front view showing a first embodiment of an on-off valve according to the present invention Sectional view along the line II-II in FIG. (I) is a cross-sectional view taken along line III-III in FIG. 2, and (II) is a cross-sectional view showing a state in the middle of closing of the valve body. (I) is sectional drawing which shows the other example of the air injection hole formed in the valve body, (II) is sectional drawing which shows the closed state of a valve body (I) is sectional drawing which shows the other example of the sealing means in the closed state of a valve body, (II) is sectional drawing which shows the closed state of a valve body Longitudinal front view showing a second embodiment of the on-off valve according to the present invention Sectional drawing along the VII-VII line of FIG. Longitudinal front view showing a third embodiment of the on-off valve according to the present invention Sectional view along line IX-IX in FIG. Longitudinal front view showing a fourth embodiment of the on-off valve according to the present invention

Explanation of symbols

11 Valve body 12 Seat ring 13 Channel 14 Valve body 15 Valve rod 18 Air supply hole 19 Air injection hole 25 Seat ring 30 Air chamber 31 Air injection hole 41 Valve body 42 Channel 43 Valve plate 50 Seal storage space 51 Seal member 52 Circular hole 53 Valve body insertion hole 54 Air supply hole 55 Semicircular outer peripheral surface 56 Air injection hole 58 Air chamber 59 Air injection hole

Claims (5)

A circular valve body for opening and closing the flow path is incorporated into the powder flow path formed inside the cylindrical valve body, and the valve body is rotated by rotating the valve rod provided on the valve body. In the open / close valve for the powder flow path that closes the flow path by contacting the seat ring provided along the flow path inner peripheral surface of the valve body with the outer peripheral portion of the valve body,
An air supply hole that extends in the radial direction and opens at the end face of the valve rod, and a compressed air supplied to the air supply hole that extends radially from the center of the valve body and communicates with the air supply hole. An on-off valve for a powder passage, wherein a plurality of air injection holes for injecting radially outward from the outer periphery of the valve body are formed.   The air injection hole portion of the air injection hole is provided with an inclined hole for injecting high-pressure air that communicates with the air injection hole and is diverted from the air injection hole from the outer peripheral portions of both side surfaces of the valve body to the obliquely outward direction. The on-off valve for a powder passage according to claim 1. A circular valve body for opening and closing the flow path is incorporated into the powder flow path formed inside the cylindrical valve body, and the valve body is rotated by rotating the valve rod provided on the valve body. In the open / close valve for the powder flow path that closes the flow path by contacting the seat ring provided along the flow path inner peripheral surface of the valve body with the outer peripheral portion of the valve body,
An annular air chamber is formed between the outer peripheral surface of the seat ring and the inner peripheral surface of the flow path of the valve body, and compressed air supplied to the air chamber is supplied to the seat ring from the valve element abutting portion of the seat ring. An on-off valve for a powder passage, wherein a plurality of air injection holes for injecting the fluid into the passage are formed at intervals in the circumferential direction. The valve body is provided with a circular flow path for powder flow and a seal storage space that opens across the flow path in the radial direction and opens at a part of the outer periphery of the valve body. A circular hole and a valve body insertion hole extending from a part of the outer periphery to the circular hole are formed coaxially with the flow path, and the valve plate is slidably inserted into the valve body insertion hole. In the open / close valve for the powder flow path, which slides toward the hole and closes the flow path by bringing the semicircular outer peripheral surface of the tip of the valve plate into close contact with the inner periphery of the circular hole,
Compressed air that is supplied to the air supply hole that extends radially from the center of curvature of the semicircular outer peripheral surface and communicates with the air supply hole. And a plurality of air injection holes for injecting the gas from a semicircular outer peripheral surface radially outward. The valve body is provided with a circular flow path for powder flow and a seal storage space that opens across the flow path in the radial direction and opens at a part of the outer periphery of the valve body. A circular hole and a valve body insertion hole extending from a part of the outer periphery to the circular hole are formed coaxially with the flow path, and the valve plate is slidably inserted into the valve body insertion hole. In the open / close valve for the powder flow path, which slides toward the hole and closes the flow path by bringing the semicircular outer peripheral surface of the tip of the valve plate into close contact with the inner periphery of the circular hole,
A semicircular air chamber is formed between the outer peripheral surface of the circular hole forming portion of the seal member and the inner peripheral surface of the seal housing space, and compressed air supplied to the air chamber is supplied to the seal member by a half of the valve plate. An on-off valve for a powder passage, wherein a plurality of air injection holes for injecting toward a circular outer peripheral surface are formed at intervals in the circumferential direction.

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