WO2016030956A1

WO2016030956A1 - Sprinkler head

Info

Publication number: WO2016030956A1
Application number: PCT/JP2014/072214
Authority: WO
Inventors: 蔵寿佐々木
Original assignee: 千住スプリンクラー株式会社
Priority date: 2014-08-26
Filing date: 2014-08-26
Publication date: 2016-03-03
Also published as: TW201607583A

Abstract

The present invention addresses the problem of providing a sprinkler head that has strength, durability or thermal conductivity and has been made lighter. A sprinkler head (S1, S2, S3), which is provided with a main body (1, 61, 101) inside which a nozzle for passing fire-extinguishing water is formed, a valve (2, 63, 103) for closing the outlet of the nozzle, and a heat-sensitive decomposing section (3, 50, 65, 105) secured to the main body for holding the valve on the outlet of the nozzle and in which the heat-sensitive decomposing section comprises a low melting point alloy (33, 51, 75, 112) that melts due to the heat of a fire. In the sprinkler head, a material comprising carbon nanotubes is used for a constituent part of the heat-sensitive decomposing section. As a result, it is possible to configure a part that is lighter than prior metal parts and for which strength and thermal conductivity performance have been improved over prior resins.

Description

Sprinkler head

The present invention relates to a fire extinguishing sprinkler head.

The sprinkler head is installed on the ceiling or wall in the building. The sprinkler head has a nozzle that can be connected to a pipe installed on the back of the ceiling or the inside of the wall on one end side, and a thermal decomposition section is provided on the other end side. During normal times, the thermal decomposition part supports a valve for closing the nozzle. On the extension of the discharge direction of the nozzle, a deflector that scatters the fire extinguishing liquid discharged from the nozzle around is provided.

In such a conventional sprinkler head, when a fire occurs, first, the thermal decomposition section is decomposed by the heat of the fire. The valve that has been pressed and supported by the thermal decomposition unit loses its supporting force, receives the water pressure in the piping, and is detached from the valve seat and falls off the outside of the main body. The water in the pipe is discharged from the open nozzle, and the discharged water collides with the deflector and scatters to the surroundings to extinguish the fire. One example of a conventional sprinkler head is described in Patent Document 1.

Sprinkler heads are mainly composed of metallic materials because they require a service life of several decades, heat resistance in the event of a fire, and thermal conductivity that absorbs heat from the fire and transfers it to the thermal decomposition unit. Yes.

On the other hand, in recent years, construction work in the construction industry has been labor-saving and shortened in delivery time, and sprinkler heads have been demanded to reduce the burden on workers and to reduce transportation costs and construction costs by reducing the size and weight.

As a means to reduce the weight of the sprinkler head, it is conceivable to use resin parts, but the use of resin materials has problems in strength, durability, heat resistance, thermal conductivity, etc. Not reached.

Japanese Patent Laid-Open No. 7-284545

In view of the above problems, an object of the present invention is to provide a sprinkler head that has strength, durability, or thermal conductivity and is reduced in weight.

In order to achieve the above object, the present invention provides the following sprinkler head.
That is, it comprises a main body having a nozzle through which fire-extinguishing water passes, a valve that closes the outlet of the nozzle, and a thermal decomposition section that is locked to the main body and holds the valve at the outlet of the nozzle. Is a sprinkler head that uses a low melting point alloy that melts by the heat of a fire and uses a material containing carbon nanotubes as a component of the thermal decomposition part.

By using a material containing carbon nanotubes for the component parts of the sprinkler head, the effect of achieving both durability and weight reduction and improving the heat conduction performance can be obtained. The effects of carbon nanotubes include improved heat conduction performance, improved mechanical strength, improved corrosion resistance, and the like. As a specific embodiment of carbon nanotubes, the coating formed by applying carbon nanotubes to a component is brought into direct contact with a low melting point alloy, or a coating made of carbon nanotubes is formed on the surface of the component, so that Can be improved, and heat transfer loss between a plurality of components can be reduced.

Furthermore, the sprinkler head has been installed in the building for a long period of time, and if corrosion products are generated on the surface of the parts of the thermal decomposition part due to corrosion, the parts adhere to each other and prevent the decomposition operation of the thermal decomposition part. There is a fear. On the other hand, the generation of corrosion products can be prevented by applying a coating of carbon nanotubes, and the operational reliability of the sprinkler head can be maintained over a long period of time.

In addition, since a load for closing the nozzle is always applied to the thermal decomposition part, it is necessary to have a mechanical strength that can withstand the load, so conventionally metal parts have been used. The use of a resin material containing carbon nanotubes can achieve both strength and weight reduction. Further, in order to improve the strength, a fine metal can be contained in the resin material. When a low-melting-point alloy is used as a fine metal, the low-melting-point alloy melts and becomes liquid due to heat during molding, so that the fluidity of the material inside the mold is good, the moldability is good, and the parts have high dimensional accuracy Can be manufactured.

On the other hand, when a material having a good thermal conductivity such as copper, brass, or aluminum is mixed as the fine metal contained in the resin material, the thermal conductivity is improved. Furthermore, when a metal plate is embedded in the above-described material having good thermal conductivity and a part is molded, heat absorbed by the surface of the part can be transmitted to the metal plate. Further, a part of the metal plate can be exposed on the surface of the component, and the exposed portion can be joined to another component by a low melting point alloy.

Alternatively, the strength of the component can be improved by mixing fine steel pieces such as stainless steel or glass fiber as the metal contained in the resin material. Further, stainless steel and glass fiber have a heat insulating effect because they have poor heat conduction performance compared to iron and copper.

When a coating film having thermal conductivity is formed on the surface of the component having the above-described heat insulating action, it is possible to make it difficult for heat absorbed by the surface of the coating film to be transmitted to the component. As a specific example of the coating, a coating made of copper plating or carbon nanotubes can be used.

Parts coated with carbon nanotubes as described above and parts formed from resin materials containing carbon nanotubes are not only used for sprinkler head components but also for sprinkler head accessories, such as sprinkler head covers and sealing plates. Is also applicable. As a specific example, a sprinkler head cover attached to a sprinkler head includes a retainer connected to the sprinkler head and a cover plate that covers the sprinkler head, and the cover plate and the retainer are low melting point alloys that are melted by the heat of a fire. Therefore, by using a material containing carbon nanotubes for the cover plate, it is possible to improve the thermal conductivity to the low melting point alloy and to reduce the weight of the cover plate.

According to the sprinkler head described above, by using a material containing carbon nanotubes for the sprinkler head components, it is possible to realize a sprinkler head that has strength, durability, or thermal conductivity and is reduced in weight. Can do.

Sectional drawing of the sprinkler head of 1st Embodiment. The exploded sectional view of a valve, a holder, and an elastic member. (A) Exploded perspective view of link, (b) Perspective view of link (after pasting with low melting point alloy). Sectional drawing of the sprinkler head of 2nd Embodiment. The principal part sectional drawing of FIG. FIG. 6 is an exploded cross-sectional view of FIG. 5. Sectional drawing of the Example which provided the film on the surface of the lower piece. Sectional drawing of the sprinkler head of the modification of 2nd Embodiment. Sectional drawing of the sprinkler head of 3rd Embodiment. The top view of the cover plate of the sprinkler head of FIG. Sectional drawing before the connection of the cover plate part of the sprinkler head of FIG.

First embodiment (FIGS. 1 to 3)
The sprinkler head S1 of the present invention includes a main body 1, a valve 2, a thermal decomposition unit 3, a holder 4, and an elastic member 5.

The main body 1 is cylindrical and has a nozzle 11 inside. A male screw 12 is formed outside the main body 1, and the male screw 12 is screwed into a female screw of a fire extinguishing equipment pipe (not shown). A valve seat 13 is formed at the discharge side end portion 11 a of the nozzle 11. The valve seat 13 is formed as a recess 13 that is recessed on the nozzle 11 side, and includes a bottom surface 13a and an inner peripheral surface 13b.

The main body 1 is provided with two

arms

14 and 14 extending in the direction of discharging water as “extinguishing liquid” discharged from the nozzle 11 from the vicinity of the valve seat 13. The

arms

14, 14 are curved and extend from the vicinity of the valve seat 13 and are connected on the extension of the central axis of the nozzle 11, and the connecting portion is a boss 15. The boss 15 has a female screw 16 formed on a line AA that is the central axis of the nozzle 11. A set screw 17 having no screw head is screwed to the female screw 16.

A disc-shaped deflector 18 is installed at the tip of the boss 15. A claw that is continuous in a wavy shape is formed on the peripheral edge 18 a of the deflector 18.

The valve 2 has a disk shape, and a sealing material 21 is provided on the surface on the nozzle 11 side. In the present embodiment, a sealing material 21 made of a fluororesin sheet is attached to the valve 2 with an adhesive and is configured integrally with the valve 2.

A step 22 and a hole 23 are formed on the opposite side of the surface on which the sealing material 21 is installed. The bullet body 5 is placed on the stepped portion 22. A hole 23 is formed in the surface of the stepped portion 22, and a convex portion 42 of the holder 4 described later is inserted into the hole 23.

The thermal decomposition unit 3 includes a link 32, a low melting point alloy 33, a lever 34, and a support column 35.

The link 32 is configured by bonding two thin metal plates 32 a with a low melting point alloy 33. It has two holes 32b in a state where the link 32 is bonded (see FIG. 3B). The lever 32 and the support column 35 are inserted into the hole 32b and engaged with the edge of the hole 32b.

A coating containing carbon nanotubes is applied to the surface of the link 32 and a coating 130 is applied. Since the heat conduction performance is improved by the coating 130, the low melting point alloy 33 is melted and the sprinkler head S1 can be operated at an early stage after the occurrence of a fire. Further, since the corrosion resistance is improved by the coating 130, it is possible to prevent the corrosion product from being generated in the link 32.

The lever 34 is L-shaped, one end of which is bent and the hole 32b of the link 32 is locked. The set screw 17 is engaged with the recess 34a formed at the other end, and the support column 35 is engaged with the groove 34b formed on the opposite surface of the recess 34a.

The support column 35 has a strip shape, the upper end is engaged with the groove 34 b of the lever 34, and the lower end is engaged with the recess 41 of the holder 4 installed on the valve 2. A protrusion (not shown) for locking the hole 32 b of the link 32 is provided at the intermediate portion of the support column 35. In FIG. 1, the set screw 17 and the recess 34a of the lever 34, the holder 4 and the valve 2 are installed on the line AA which is the central axis of the nozzle. The position is slightly separated, and the column 35 is installed with a slight inclination with respect to the line AA.

When the set screw 17 is moved to the lever 34 side, the support column 35 presses the holder 4 and the valve 2 toward the nozzle 11 via the lever 34 to close the nozzle 11. Further, a force that rotates clockwise with the groove 34 engaged with the column 35 acting as a fulcrum acts on the lever 34. As a result, a force that rotates in the upper left direction acts on the end of the lever 34 engaged with the link 32, but the lever 34 does not rotate because it is engaged with the link 32.

When the low melting point alloy 33 is melted by the heat of the fire, the two

metal plates

32a, 32a constituting the link 32 become movable, and the lever 34 rotates clockwise to pull the

metal plates

32a, 32a apart. As a result, the thermal decomposition unit 3 is decomposed and the valve 2 is separated from the nozzle 11 and the nozzle 11 is opened.

The holder 4 has a disk shape and is installed between the valve 2 and the thermal decomposition unit 3. A concave portion 41 supported by one end side of the thermal decomposition unit 3 is formed on one side of the holder (upper surface in the drawing). A convex portion 42 inserted through the hole 23 of the valve 2 is formed on the surface opposite to the surface where the concave portion 41 is formed. In the drawing, the convex portion 42 is inserted into the hole portion 23, and a movable gap 6 is provided between the tip of the convex portion 42 and the bottom surface of the hole portion 23.

The elastic member 5 is a disc spring and has an action of pressing the valve 2 to the nozzle 11 side and pressing the holder 4 to the thermal decomposition unit 3 side. A load is applied to the elastic member 5 by a set screw 17. That is, when the set screw 17 is screwed in the direction of the nozzle 11, the elastic member 5 is pressed from the tip of the set screw 17 through the thermal decomposition part 3 and the holder 4, and the elastic member 5 is completely crushed by elastic deformation. Although it is not, it will be in the state crushed by the predetermined pressure with which the movable gap 6 remains. When the elastic member 5 is in the crushed state in this way, it is possible to obtain a state in which a closing load is applied to the valve 2 and the discharge side end portion 11a of the nozzle 11 is closed by the valve 2.

In addition, since the disk spring which comprises the elastic member 5 is small in size, there exists an advantage which can be easily integrated in the sprinkler head S1 and can be elastically deformed with a big load. Specifically, when the pressure receiving area from the nozzle 11 of the valve 2 is 1 cm ² , if the load by which the disc spring 5 is displaced is set to about 500 N, the disc spring will be when the water pressure in the nozzle 11 reaches about 5 MPa. 5 is elastically deformed so that the valve 2 can be separated from the valve seat 13 and the fire extinguishing liquid in the nozzle 11 can escape to the outside.

Second Embodiment (FIGS. 4 to 7)
The second embodiment is a sprinkler head in which a coating containing carbon nanotubes is applied to the components of the thermal decomposition section. The sprinkler head S2 of the second embodiment shown in FIG. 4 includes a main body 101, a frame 102, a valve 103, a deflector unit 104, a thermal decomposition unit 105, and a pressing piece 106. In addition, about the part with the same structure as 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

The configuration of the sprinkler head S2 of the second embodiment is the same as that described in Japanese Patent Application Laid-Open No. 2000-79182, and description of portions that are not very relevant to the present invention is omitted. In the sprinkler head S2, only the thermal decomposition unit 105 and the pressing piece 106 are disposed so as to protrude from the ceiling to the indoor side.

The thermal decomposition unit 105 includes a cylinder 110, a plunger 111, and a low melting point alloy 112. The cylinder 110 has a cylindrical shape, and the upper end is closed by a flat surface. A low melting point alloy 112 is accommodated in the cylinder 110. A hole 113 formed through the low melting point alloy 112 is formed at the center of the upper end plane of the cylinder 110.

The plunger 111 has a shaft portion 114 and a disc-shaped flange portion 115 formed at the lower end thereof. The shaft portion 114 is inserted into the hole 113 so that the upper surface of the flange portion 115 is in contact with the surface of the low melting point alloy 112. A male screw 116 is provided at the upper end of the shaft portion 114.

The holding piece 106 includes an upper piece 121, a lower piece 122, and a leaf spring 123.

The diameters of the circular upper piece 121 and the circular lower piece 122 are the same, and are slightly smaller than the inner diameter of the inner flange 124 formed at the lower end of the cylindrical frame 102. At the center of the upper piece 121, a female screw 125 that is screwed with the male screw 116 of the shaft portion 114 of the plunger 111 is screwed.

A hole through which the shaft portion 114 can be easily inserted is formed in the center of the lower piece 122. The upper part of the lower piece 122 is recessed, and the leaf spring 123 is accommodated therein. A circular recess 126 for accommodating the cylinder 110 is formed in the lower part.

The leaf spring 123 has a hole through which the shaft portion 114 can be inserted at the center of the disc-shaped bottom surface 127. A plurality of spring portions 128 are installed from the periphery of the bottom surface 127 so as to extend obliquely at equal intervals. The spring parts 128 are spaced apart by a gap. In the unloaded state, the tip of the spring portion 128 is disposed inside the outer edges of the upper piece 121 and the lower piece 122.

The leaf spring 123 is installed between the upper piece 121 and the lower piece 122, and the shaft portion 114 of the plunger 111 is inserted into each center hole. When the male screw 116 of the shaft portion 114 is screwed into the female screw 125 of the upper piece 121, the spring portion 128 of the leaf spring 123 is crushed between the upper piece 121 and the lower piece 122, and the tip of the spring portion 128 is moved. It will be in the state which protruded from the outer edge of the upper piece 121 and the lower piece 122. FIG. The protruding spring portion 128 is engaged with the inner flange 124 of the frame 102 as shown in FIGS.

The lower piece 122 is formed of a resin in which carbon nanotubes and fine pieces such as stainless steel and glass fiber are mixed. Thereby, compared with a general resin, strength and heat resistance are improved. The lower piece 122 is a part that is constantly subjected to a load by the leaf spring 123, but has higher durability than general resin due to its improved strength.

Further, by forming the coating 130 on the surface of the lower piece 122 and the inner surface of the recess 126, a heat conducting portion can be provided. The heat absorbed by the coating 130 can be transferred to the low melting point alloy 112 through the cylinder 110, and the heat conduction performance is improved. As a specific example of the coating 130, a copper plating or a carbon nanotube layer can be used.

Further, as shown in FIG. 7, when a coating 130 having thermal conductivity is formed on and around the inner surface of the recess 126 of the lower piece 122 and the inside of the recess 126 is filled with the low melting point alloy 112, the low temperature is directly reduced from the coating 130. Heat is conducted to the melting point alloy 112 so that the heat can be efficiently transferred to the low melting point alloy 122. Thereby, the cylinder 110 can be eliminated by the recess 126 and the coating 130.

Modified example of the second embodiment (FIG. 8)
A modification of the second embodiment shown in FIG. 8 is a sprinkler head described in Japanese Patent Laid-Open No. 11-299921. In FIG. 8, a coating film 130 (not shown) of carbon nanotubes is applied to the surfaces of the cylinder 52 containing the low melting point alloy 51 contained in the thermal decomposition section 50, the cover 53 connected to the cylinder 52, and the heat collecting plate 54. Thus, the heat conduction performance is improved. In particular, heat transfer loss can be reduced by the close contact of the coating 130 of each component at the connecting portion between the cylinder 52, the cover 53, and the heat collecting plate 54.

Further, when the low melting point alloy 51 is formed in a cylindrical shape and accommodated in the cylinder 52, the coating 130 made of carbon nanotubes is also formed on the surface of the low melting point alloy 51, whereby the low melting point alloy 51 and the cylinder are formed. The heat transfer loss between 52 can be reduced.

Third Embodiment (FIGS. 9 to 11)
The sprinkler head of the third embodiment shown in FIG. 9 includes a main body 61, a frame part 62, a valve 63, a deflector part 64, a thermal decomposition part 65, a support cup 66, and a cover plate part 7.

The configuration of the sprinkler head according to the third embodiment is the same as that described in Japanese Patent Application Laid-Open No. 2011-218062, and description of portions that are not very relevant to the present invention is omitted. In addition, about the part with the same structure as 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

The sprinkler head S3 of FIG. The cover plate portion 7 includes a disc-shaped cover plate 71 and a cylindrical retainer 72. The cover plate 71 is formed from a resin material in which carbon nanotubes and fine metals are mixed.

As the resin material, a resin pellet in which carbon nanotubes or metal are mixed is used, or the resin pellet is mixed with carbon nanotubes or metal powder and molded by a mold. In any method, after molding, the carbon nanotube and the metal are mixed in the resin.

Further, when a low melting point alloy is used as the resin material, the low melting point alloy is melted by heat during molding, so that the fluidity of the material inside the mold is improved and the moldability is improved. On the other hand, when a material having a good thermal conductivity such as copper, brass, or aluminum is mixed, the thermal conductivity is improved. The cover plate 71 made of such a material has a thickness larger than that of a conventional product made of a metal plate and is hard to be deformed, so that it is possible to prevent the cover plate 71 from being deformed during mounting. . Further, the shape of the cover plate 71 can be freely formed by a mold, and in addition to a normal disk shape, it can be a three-dimensional shape such as a rectangular or hexagonal cover plate or a dome shape. You can also.

The surface of the cover plate 71 is exposed in the room. Therefore, the cover plate 71 colored in an arbitrary color can be manufactured by mixing the pigment at the time of molding.

A metal plate 73 is embedded and installed on the back surface of the cover plate 71. Copper or brass is used as the metal plate 73, and in the drawing, it is installed at three locations at equal intervals in the vicinity of the periphery of the cover plate 71. The metal plate 73 is joined to a leg 74 formed at the lower end of the retainer 72 by a low melting point alloy 75.

By installing the metal plate 73, the heat absorbed on the surface of the cover plate 71 can be transmitted to the metal plate 73 through the metal component inside the cover plate 71, and the low temperature bonded to the surface of the metal plate 73 can be obtained. Melting of the melting point alloy 75 can be promoted.

The retainer 72 has a cylindrical shape as described above, and a leg 74 joined to the lower end of the retainer 72 via the low melting point alloy 75 and the metal plate 73 of the cover plate 71 is provided. The legs 74 are installed corresponding to the positions of the metal plates 73 and are arranged at equal intervals in the same manner as the cover plate 71 of FIG.

On the outer side of the cylindrical portion of the retainer 72, a plurality of claws 76 that can be engaged with the spiral groove 68 formed on the side surface of the support cup 6 are provided so as to protrude. The claw 76 is engaged with the spiral groove 68 by fitting the claw 76 into the support cup 6. When the cover plate portion 7 is rotated in this state, the retainer 72 is accommodated inside the support cup 6 by moving the claw 76 along the spiral groove 68.

A flange 77 extended outward is formed between the leg 74 and the claw 76 of the retainer 72. A slight gap is provided between the flange 77 and the edge of the cover plate 71. The position is adjusted by rotating the cover plate portion 7 so that the flange 77 is close to the lower surface of the ceiling board C.

The cover plate portion 7 configured as described above is installed on the sprinkler head S3. When a fire occurs, the low-melting-point alloy 75 has heat absorbed from the surface and heat absorbed from the surface of the cover plate 71 transmitted to the metal plate 73 by the carbon nanotubes and metal components inside the cover plate 71, and the low-melting-point alloy 75 Promotes melting of 75.

When the low melting point alloy 75 is melted, the cover plate 71 is dropped, and the deflector portion 64 and the thermal decomposition portion 65 of the sprinkler head S3 are exposed. The operation of the thermal decomposition unit 65 is promoted by exposure of the heat of the fire to the thermal decomposition unit 65, and the thermal decomposition unit 65 is decomposed. Then, the valve 63 supported by the thermal decomposition unit 65 drops and water is discharged from the nozzle 11 inside the main body 61 connected to the water supply pipe, and the water collides with the deflector unit 64 and scatters in all directions to cause a fire. Crush.

In the above embodiment, the cover plate 71 is made of a resin material containing carbon nanotubes. However, the coating 130 can be applied to the components of the thermal decomposition portion 65.

S1, S2, S3 Sprinkler head
1, 61, 101 body
2, 63, 103 Valve
3, 50, 65, 105 Thermal decomposition section
4 Holder
5 Elastic members
6 Movable gap
7 Cover plate
32 links
33, 51, 75, 112 Low melting point alloy
34 lever
35 props
52, 110 cylinders
53 Cover
54 Heat collecting plate
62, 102 frames
64, 104 Deflector part
66 Support Cup
71 Cover plate
72 Retainer
73 Metal plate
74 legs
76 nails
77 Flange
106 Presser piece
111 Plunger
121 Upper piece
122 Lower piece
123 leaf spring
130 coating

Claims

A body with a nozzle through which fire-extinguishing water passes
A valve that closes the outlet of the nozzle;
A thermal decomposition part that is locked to the main body and holds the valve at the outlet of the nozzle,
A sprinkler head characterized in that the thermal decomposition part includes a low-melting-point alloy that melts by the heat of a fire, and a material containing carbon nanotubes is used as a component of the thermal decomposition part.
A main body formed with a nozzle through which fire-extinguishing water passes,
A valve that closes the outlet of the nozzle;
A sprinkler head cover is detachably attached to a sprinkler head that includes a thermal decomposition section that is locked to the main body and holds the valve at the nozzle outlet.
The sprinkler head cover includes a retainer coupled to the sprinkler head and a cover plate that covers the sprinkler head,
The cover plate and retainer are joined by a low melting point alloy that melts by the heat of the fire.
A sprinkler head characterized in that a material containing carbon nanotubes is used for a cover plate.
The sprinkler head according to claim 1 or 2, wherein a coating containing a carbon nanotube is applied to the surface of a heat transfer member that conducts heat to the low melting point alloy as the material containing the carbon nanotube.
The sprinkler head according to claim 3, wherein the coating is applied to a surface of a link joined by a low melting point alloy included in the thermal decomposition portion.
The sprinkler head according to claim 3, wherein the coating is applied to the surface of a part containing a low melting point alloy contained in the thermal decomposition part.
The sprinkler head according to any one of claims 1 to 5, wherein the coating is applied to a surface of the low melting point alloy.
The sprinkler head according to claim 1 or 2, wherein a carbon nanotube and a fine metal are contained in a resin as the material containing the carbon nanotube.
The sprinkler head according to claim 7, wherein a low melting point alloy is used as the metal.
The sprinkler head according to any one of claims 2 to 8, wherein a metal plate is embedded in the cover plate.
The sprinkler head according to claim 9, wherein a part of the metal plate is exposed on a surface of the cover plate.