Pressure relief return valve and spray system

Abstract

The present application provides a kind of pressure relief backflow valve, including valve body and end cover, pressure relief pipe, valve body includes cavity and valve core, cavity includes first cavity section, second cavity section and third cavity section, cavity also includes air inlet and feed inlet, sliding seat is arranged in first cavity section, isolation component is arranged in third cavity section, pressure relief pipe includes connecting hole and pressure relief hole, valve core includes one head end, head end can be movably closed or opened connecting hole, a spring is used to exert tension to sliding seat, valve body also includes a recess part, isolation component includes a center valve seat, center valve seat includes a through hole corresponding with recess part, at least a part of valve core can be presented through the through hole, one aspect gas source is the acting force of valve core movement, so that the pressure fluctuation response of the pressure relief backflow valve of the present application to gas source will be more direct and fast, two aspects users can easily observe or detect the action of valve core, to improve the efficiency of overhaul, the present application simultaneously provides the spraying system of application this pressure relief backflow valve.

Description

TECHNICAL FIELD

[0001] The present application relates to a pressure relief return valve and a spraying system. BACKGROUND

[0002] The pressure relief return valve is a valve that protects the system from being damaged due to excessive pressure. Once the medium pressure in the system pipeline or device exceeds the set value, it will automatically release the pressure to achieve the purpose of safety protection.

[0003] The existing pressure relief return valve, such as the document number CN217683438U, named a return valve of a hot melt adhesive machine, the document number CN102599819A, named a pressure relief return valve for a coffee machine, the document number CN218347995U, named a sanitary pressure relief return valve, and other patent documents disclose the structure: these pressure relief return valves include a flow channel with a medium inlet and a pressure relief port and a pressure relief assembly, the pressure relief assembly includes a valve ball or valve rod that can move under the action of elastic force to close or open the flow channel, when the medium pressure in the flow channel is too high, the valve ball or valve rod overcomes the elastic force to release the medium from the pressure relief port, thereby reducing the pressure or making the medium pressure in the flow channel within a suitable range. In this common structure, the following problems exist:

[0004] 1. In some systems driven by a gas source, such as a spraying system, the gas source is prone to pressure fluctuations. When the gas source drives the spraying device, the valve ball or valve rod is moved by the medium, making the response to gas pressure fluctuations slow and unable to accurately control the medium pressure.

[0005] 2. In this structure, the valve rod or valve ball is located inside the valve body, and it is difficult to know the movement of the valve rod or valve ball. Even in maintenance or repair, it is difficult to judge the displacement of the valve rod or valve ball, or at least the pressure relief return valve needs to be connected to a complete system to judge the movement of the valve rod or valve ball, making maintenance very inconvenient. SUMMARY

[0006] Therefore, the present application provides a pressure relief return valve to solve the above technical problems.

[0007] A pressure relief return valve, comprising a valve body and end covers arranged on both sides of the valve body, a pressure relief pipe:

[0008] The valve body comprises a cavity and a valve core arranged in the cavity, the cavity comprises a first cavity section facing the end cover direction, a second cavity section facing the pressure relief pipe direction, and a third cavity section connecting the first cavity section and the second cavity section, the cavity further comprises an air inlet communicating with the first cavity section and a feed inlet communicating with the second cavity section, the first cavity section further comprises a sliding seat connected with the valve core, and the third cavity section further comprises a separation assembly for separating the first cavity section and the second cavity section;

[0009] The end cover comprises a containing space;

[0010] The pressure relief pipe comprises a connecting hole and a pressure relief hole in communication with the second cavity section;

[0011] The valve core comprises a head end, the head end is movable to close or open the connecting hole, a spring is arranged in the containing space to apply tension to the sliding seat, the valve body further comprises a groove part, the isolation assembly comprises a center valve seat, the center valve seat comprises a through hole corresponding to the groove part, and at least a part of the valve core is exposed through the through hole.

[0012] The center valve seat comprises an inner hole, the valve core is arranged in the inner hole, and the valve core is in airtight connection with the center valve seat.

[0013] The third cavity section comprises a first cavity, the center valve seat comprises a first sealing section in the first cavity, the first sealing section is in airtight connection with the inner wall of the first cavity, the inner hole comprises a first inner hole section, the center valve seat is provided with a positioning groove at the first sealing section, a first sealing gasket is sleeved on the valve core and located in the positioning groove, and a sealing ring is arranged between the first sealing gasket and the positioning groove.

[0014] The third cavity section comprises a second cavity, the center valve seat comprises a second sealing section in the second cavity, the second sealing section is threadedly connected to the second cavity, and the isolation assembly further comprises a sealing device arranged between the center valve seat and the second cavity section, the sealing device comprises at least one second sealing gasket adjacent to the second cavity section and an inner valve seat, and the inner valve seat abuts against the second sealing gasket and limits the second sealing gasket in the second cavity.

[0015] An elastic gasket is further arranged between the center valve seat and the inner valve seat, the second sealing gasket has a plurality of second sealing gaskets, and the plurality of second sealing gaskets are sequentially sleeved on the valve core.

[0016] The pressure relief pipe comprises a pressure relief valve seat, the pressure relief valve seat comprises a connecting hole, the connecting hole comprises a first connecting hole and a second connecting hole in a stepped shape, the first connecting hole has a larger diameter than the outer diameter of the valve core, and the second connecting hole has a smaller diameter than the outer diameter of the head end.

[0017] The pressure relief pipe further comprises a connecting seat and a pressure relief pipe, the connecting seat is in a tubular shape, one end of the connecting seat is connected to the valve body, the other end of the connecting seat is provided with an inner thread and an outer thread, the pressure relief valve seat is connected through the inner thread of the connecting pipe, and the pressure relief pipe is connected through the outer thread of the connecting seat.

[0018] The connecting pipe comprises an end face, the pipe wall section of the pressure relief valve seat is T-shaped, comprising a first connecting part and a second connecting part, the outer wall of the first connecting part is provided with external threads for connecting with the internal threads of the connecting seat, the pressure relief valve seat is in airtight connection with the connecting seat, the second connecting part comprises an inner side face and an outer side face, wherein the inner side face abuts against the end face of the connecting seat, the pressure relief pipe comprises an inner abutting face, when the pressure relief pipe is connected to the connecting seat through threads, the inner abutting face of the pressure relief pipe abuts against the outer side face of the second connecting part.

[0019] The through hole penetrates the center valve seat.

[0020] The application also provides a spraying system, which comprises a gas source, a spraying device, the pressure relief backflow valve and a spray head.

[0021] The pressure relief backflow valve comprises a valve body, end covers arranged on both sides of the valve body, a pressure relief pipe, a cavity and a valve core, the cavity comprises a first cavity section, a second cavity section and a third cavity section, the cavity further comprises an air inlet and a material inlet, a sliding seat is arranged in the first cavity section, an isolation assembly is arranged in the third cavity section, the pressure relief pipe comprises a connecting hole and a pressure relief hole, the valve core comprises a head end, the head end can movably close or open the connecting hole, a spring is arranged to apply tension to the sliding seat, the valve body further comprises a groove part, the isolation assembly comprises a center valve seat, the center valve seat comprises a through hole arranged corresponding to the groove part, at least a part of the valve core can pass through the through hole, on one hand, the gas source is the acting force for the movement of the valve core, so that the pressure relief backflow valve can directly and quickly respond to the fluctuation of the gas source pressure, on the other hand, the gas enters the area different from the medium, and is isolated, so that the temperature and other factors of the medium cannot affect the gas side, on the third hand, the user can easily observe or detect the movement of the valve core, thereby improving the maintenance efficiency, and the application further provides a spraying system using the pressure relief backflow valve. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A perspective view of the pressure relief backflow valve of the embodiment of the application;

[0023] Figure 2 A rear perspective view of the pressure relief backflow valve; Figure 1

[0024] Figure 3 A top view of the pressure relief backflow valve; Figure 1

[0025] Figure 4 A top view of the pressure relief backflow valve; Figure 3 ​​A-A sectional view;

[0026] Figure 5 A Figure 4 B zone enlarged view;

[0027] Figure 6 A Figure 4 C zone enlarged view;

[0028] Figure 7 A spraying system schematic diagram using the pressure relief backflow valve shown in Figure 1

[0029] Figure illustration element description:

[0030] Valve body 10; cavity 100; first cavity section 101; second cavity section 102; third cavity section 103; feed inlet 104; discharge outlet 105; medium section 11; inlet section 12; connecting section 13; recess part 14; sliding seat 15; locking nut 16; center valve seat 20; through hole 201; second sealing washer 21; inner valve seat 23; elastic washer 24; first sealing washer 25; end washer 26; pressure relief pipe 30; pressure relief hole 301; pressure relief port 302; pressure relief valve seat 31; connecting hole 310; first connecting part 311; second connecting part 312; first connecting hole 313; second connecting hole 314; connecting seat 32; inner thread 321; outer thread 322; end cover 40; containing space 400; air hole 401; spring 41; valve core 50; valve ball 51; inlet pipe 60; plug 70; sealing ring 71, 72, 73, 74, 75, 76; pressure relief backflow valve 900; air source 901; spraying device 902; spray head 903. DETAILED DESCRIPTION

[0031] Please refer to Figures 1-2 , the embodiment of the present application provides a kind of pressure relief backflow valve 900, for being used in such as spraying system, to make the medium pressure of spraying system be in controlled range, the pressure relief backflow valve 900 described, including valve body 10 and the end cover 40 being arranged in the both sides of valve body 10, pressure relief pipe piece, the valve body 10 is provided with inlet, feed inlet 104 and pressure relief port 302.

[0032] To make it easier to describe the pressure relief backflow valve 900 of the present application, please refer to Figure 7 , in Figure 7 ​A spraying system using the pressure relief backflow valve 900 is shown in the following figure, which includes a gas source 901, a spraying device 902, the pressure relief backflow valve 900 and a spray head 903. The gas source 901 is used to provide pneumatic power for the spraying device 902, so that the spraying device 902 can deliver medium to the spray head 903, and the medium is sprayed from the spray head 903 to a predetermined position. It can be understood that the medium is not limited to a material, and in some embodiments, the medium can be paint, grease, hot melt adhesive or other liquid or semi-solid fluid.

[0033] The spraying device 902 includes an inlet and an outlet. The inlet is connected to the gas source 901 by a pipeline, and the outlet is connected to the feed port 104 by a pipeline. At the same time, the gas source 901 is also connected to the air inlet by a pipeline, and the spray head 903 is connected to the outlet by a pipeline or connected to the pipeline between the outlet and the pressure relief backflow valve 900. It can be understood that when the pressure of the gas source 901 increases, the pressure of the medium output from the outlet also increases synchronously. In the spraying system, when the pressure of the gas source 901 increases, part of the medium is released through the pressure relief port 302 to reduce the pressure of the medium output from the outlet, thereby preventing the spraying system from being damaged or spraying too much.

[0034] It can be understood that the medium discharged through the pressure relief port 302 can also be recycled and sent back to the spraying device 902.

[0035] In the above case, the pressure relief backflow valve 900 of the present application responds more directly and quickly to the pressure fluctuations of the gas source 901, especially when the medium is a non-Newtonian fluid, which presents a more efficient response.

[0036] The following will be described in detail with reference to the accompanying drawings Figures 3-6 The pressure relief backflow valve 900 of the present application will be described in detail.

[0037] The valve body 10 includes a cavity 100 and a valve core 50 arranged in the cavity 100. The cavity 100 includes a first cavity section 101 facing the direction of the end cover 40, a second cavity section 102 facing the direction of the pressure relief pipe, and a third cavity section 103 connecting the first cavity section 101 and the second cavity section 102. The air inlet is in communication with the first cavity section 101, and the feed port 104 is in communication with the second cavity section 102. At the same time, the first cavity section 101 is also provided with a sliding seat 15 connected with the valve core 50. The third cavity section 103 is also provided with an isolation assembly for isolating the first cavity section 101 and the second cavity section 102. The valve body 10 also includes a recess portion 14. The isolation assembly includes a center valve seat 20, which includes a through hole 201 arranged corresponding to the recess portion 14. At least a part of the valve core 50 can be exposed through the through hole 201.

[0038] Specifically, the valve body 10 includes a medium section 11 on both sides of the valve body 10, an air inlet section 12, and a connecting section 13 between the air inlet section 12 and the medium section 11, wherein the connecting section 13 is the part of the valve body 10 corresponding to the groove part 14, the valve body 10 includes end faces on both ends of the valve body 10, for the convenience of description, the end face adjacent to the air inlet section 12 is referred to as the first end face, and the end face adjacent to the medium section 11 is referred to as the second end face, and the cavity 100 penetrates the first end face and the second end face.

[0039] Preferably, the valve body 10 has a central axis, and the cavity 100 also has a central axis, and the central axis of the cavity 100 is collinear with the central axis of the valve body 10.

[0040] The cavity 100 is in the shape of a stepped hole from the first end face to the second end face, and the hole diameter gradually decreases.

[0041] More specifically, the inner diameter of the first cavity section 101 is greater than the inner diameter of the third cavity section 103, and the inner diameter of the third cavity section 103 is greater than the inner diameter of the second cavity section 102.

[0042] The slide 15 is arranged in the first cavity section 101, the slide 15 is in airtight connection with the inner wall of the first cavity section 101, and the slide 15 is connected to the valve core 50, so that the slide 15 drives the valve core 50 to move synchronously when the slide 15 moves. In this embodiment, the valve core 50 further comprises a locking nut 16 at the end thereof, and the slide 15 is fixed to the valve core 50 through the locking nut 16.

[0043] The end cover 40 comprises a containing space 400, is threadedly connected to the air inlet section 12, and seals the first end face. A spring 41 is arranged between the end cover 40 and the slide 15. It can be understood that the spring 41 is used to apply an elastic tension to the slide 15. When the pressure relief backflow valve 900 is connected to the spraying system, high-pressure gas enters the first cavity section 101 through the air inlet. When the gas pressure is greater than the elastic tension applied by the spring 41 to the slide 15, the slide 15 moves towards the end cover 40, thereby driving the valve core 50 to move, so that the head end of the valve core 50 opens the connecting hole 310, and the medium is released from the connecting hole 310 and the pressure relief hole 301.

[0044] It can be understood that the distance between the end cover 40 and the first end face is adjusted, so that the size of the elastic tension applied by the spring 41 to the slide 15 is adjusted, and the air inlet pressure overcoming the elastic tension is adjusted.

[0045] In order to maintain the airtightness between the slide 15 and the inner wall of the first cavity section 101, the slide 15 is circumferentially provided with a containing groove, and a sealing ring 76 is arranged in the containing groove.

[0046] Further, the air inlet section 12 is provided with an air inlet pipe 60 connected with the air inlet.

[0047] Further, the end cover 40 is provided with a vent hole 401 communicating the containing space 400 with the atmosphere.

[0048] The pressure relief pipe member is arranged in the medium section 11 and extends away from the second end face, and comprises a connecting hole 310 communicating with the second cavity section 102 and a pressure relief hole 301, and the valve core 50 comprises a head end movably closing or opening the connecting hole 310, the medium enters the second cavity section 102 through the feed port 104, when the air inlet pressure of the air inlet is less than or equal to the elastic tension of the spring 41 applied to the sliding seat 15, the medium is closed in the second cavity section 102, and when the air inlet pressure of the air inlet is greater than the elastic tension of the spring 41 applied to the sliding seat 15, the head end opens the connecting hole 310, and the medium is released from the connecting hole 310 and the pressure relief hole 301.

[0049] In the embodiment, the pressure relief pipe member comprises a pressure relief valve seat 31, and the pressure relief valve seat 31 comprises the connecting hole 310, in the embodiment, the connecting hole 310 comprises a first connecting hole 313 and a second connecting hole 314 in a stepped shape, wherein the diameter of the first connecting hole 313 is greater than the outer diameter of the valve core 50, and the diameter of the second connecting hole 314 is less than the outer diameter of the head end, so that the head end of the valve core 50 can close the second connecting hole 314 when abutting against the second connecting hole 314.

[0050] Further, the head end of the valve core 50 further comprises a valve ball 51, and the second connecting hole 314 is opened or closed by the valve ball 51, and it can be understood that the valve ball 51 has an outer diameter greater than the diameter of the second connecting hole 314 when provided.

[0051] Further, the pressure relief valve seat 31 is further provided with a pressure relief pipe 30, and the pressure relief pipe 30 comprises a pressure relief hole 301 communicating with the connecting hole 310, and the pressure relief hole 302 is the end of the pressure relief hole 301, and preferably, the pressure relief hole 302 is a horn-shaped opening.

[0052] Further, the pressure relief pipe member further comprises a connecting seat 32 connected with the valve body 10, and the pressure relief valve seat 31 and the pressure relief pipe 30 are connected on the connecting seat 32, and specifically, the connecting seat 32 is a pipe-shaped structure, one end of which is connected with the valve body 10, and the other end is provided with an internal thread 321 and an external thread 322, the pressure relief valve seat 31 is connected through the internal thread 321 of the connecting pipe, and the pressure relief pipe 30 is connected through the external thread 322 of the connecting seat 32.

[0053] Further, the connecting pipe comprises an end face, the pressure relief valve seat 31 comprises a T-shaped pipe wall section, comprising a first connecting part 311 and a second connecting part 312, the outer wall of the first connecting part 311 is provided with external threads 322 for connecting with the internal threads 321 of the connecting seat 32, meanwhile, the first connecting part 311 is provided with a receiving groove, and a sealing ring 74 is arranged in the receiving groove, so as to realize the air-tight connection between the pressure relief valve seat 31 and the connecting seat 32, the second connecting part 312 comprises an inner side face and an outer side face, wherein the inner side face abuts against the end face of the connecting seat 32, meanwhile, the pressure relief pipe 30 comprises an inner abutting face, when the pressure relief pipe 30 is connected to the connecting seat 32 through threads, the inner abutting face of the pressure relief pipe 30 abuts against the outer side face of the second connecting part 312, that is, the second connecting part 312 is clamped by the connecting seat 32 and the pressure relief pipe 30, so as to realize the air-tight effect, in order to better realize the air-tightness, the outer side face of the second connecting part 312 is also provided with a receiving groove, and a sealing ring 75 is arranged in the receiving groove.

[0054] Through the above arrangement, on the one hand, different pressure relief pipe components can be conveniently used to adapt to different media, on the other hand, the air-tightness of the connecting faces of the pressure relief pipe components is realized, so as to maintain the sealing performance of the second cavity section 102.

[0055] Further, the first connecting hole 313 is formed around the first connecting part 311, and the second connecting hole 314 is formed around the second connecting part 312.

[0056] The third cavity section 103 is provided with an isolation assembly for isolating the first cavity section 101 and the second cavity section 102, that is, the gas in the first cavity section 101 cannot leak or flow to the second cavity section 102 from the third cavity section 103, and the medium in the second cavity section 102 cannot leak or flow to the first cavity section 101 from the third cavity section 103, the isolation assembly comprises a center valve seat 20 arranged in the third cavity section 103.

[0057] It can be understood that the center valve seat 20 comprises an inner hole, the valve core 50 is arranged in the inner hole, and the valve core 50 is air-tightly connected with the center valve seat 20, in addition, the valve core 50 can freely move in the inner hole, so as to drive the head end to move when the sliding seat 15 moves, thereby opening or closing the connecting hole 310.

[0058] Specifically, the third cavity section 103 comprises a first cavity located in the air inlet section 12, the center valve seat 20 comprises a first sealing section located in the first cavity, the first sealing section is air-tightly connected with the inner wall of the first cavity, in this embodiment, the outer wall of the first sealing section is provided with a receiving groove, and a sealing ring 73 is arranged in the receiving groove.

[0059] The inner hole comprises a first inner hole section, the center valve seat 20 is provided with a positioning groove in the first sealing section, a first sealing gasket 25 is sleeved on the valve core 50 and located in the positioning groove to realize the sealing between the valve core 50 and the inner hole.

[0060] Further, a sealing ring 72 is arranged between the first sealing gasket 25 and the positioning groove, so that the sealing between the first sealing gasket 25 and the center valve seat 20 is also realized.

[0061] Further, an end gasket 26 is further arranged outside the positioning groove, and the first sealing gasket 25 and the sealing ring 72 are limited in the positioning groove through the end gasket 26.

[0062] The third cavity section 103 comprises a second cavity in the medium section 11, the center valve seat 20 comprises a second sealing section in the second cavity, and in the embodiment, the second sealing section is threadedly connected on the second cavity, and the sealing device is further arranged between the center valve seat 20 and the second cavity section 102 to realize the sealing.

[0063] The sealing device comprises at least one second sealing gasket 21 adjacent to the second cavity section 102 and an inner valve seat 23, wherein the inner valve seat 23 is used to abut against the second sealing gasket 21 to limit the second sealing gasket 21 in the second cavity.

[0064] Further, the second sealing gasket 21 has a plurality of second sealing gaskets 21, and the plurality of second sealing gaskets 21 are sequentially sleeved on the valve core 50, and a sealing ring 71 is further arranged between the second sealing gasket 21 and the second cavity, so as to realize the sealing between the valve core 50 and the second cavity.

[0065] Further, an elastic gasket 24 is further arranged between the center valve seat 20 and the inner valve seat 23, so that the second sealing gasket 21 is kept at a predetermined position and kept sealed under the elastic tension of the elastic gasket 24.

[0066] It can be understood that, since the center valve seat 20 is threadedly connected on the second cavity, the position of the center valve seat 20 extending into the second cavity can be adjusted, so as to adjust the tension of the elastic gasket 24 on the inner valve seat 23 and the second sealing gasket 21, so as to better keep the second sealing gasket 21 pressed, on the other hand, the center valve seat 20 is threadedly connected on the second cavity, and no additional connecting device is needed at the first cavity, and at the same time, the size of the gap of the first cavity section 101 can also be adjusted by adjusting the position of the center valve seat 20 extending into the second cavity.

[0067] Further, the first sealing gasket 25 is made of rubber material to achieve better air tightness, and the second sealing gasket 21 is made of polytetrafluoroethylene to achieve the sealing effect on the medium, and the polytetrafluoroethylene also has excellent corrosion resistance, thereby maintaining the sealing of the medium.

[0068] It can be seen that the isolation assembly seals the gas and the medium on both sides, thereby isolating the gas and the medium. In practice, the above arrangement can also simultaneously avoid the influence of the temperature of the medium on the first cavity section 101, thereby achieving better response.

[0069] The center valve seat 20 further comprises a middle section between the first sealing section and the second sealing section, the middle section corresponds to the groove portion 14, and a through hole 201 is arranged in the middle section, the through hole 201 extends at least from the outside of the center valve seat 20 to the inner hole, so that at least a part of the valve core 50 can be presented through the through hole 201. The meaning of the presentation through the through hole 201 is that the user can visually observe at least a part of the valve core 50 through the through hole 201, or an optical sensor can directly detect or observe at least a part of the valve core 50 through the through hole 201. In this case, the user can easily observe or detect the action of the valve core 50, thereby avoiding the problem that the action of the valve core 50 is difficult to be observed or detected in the prior art.

[0070] Further, the depth of the groove portion 14 should be such that the middle section is completely exposed, and the through hole 201 penetrates the center valve seat 20. In this case, the action of the valve core 50 can be more easily observed or observed.

[0071] In practice, by opening the groove portion 14 on the valve body 10 and opening the through hole 201 on the center valve seat 20, the following effects are also achieved: 1. By opening the groove portion 14, the center valve seat 20 can be positioned or fixed in the groove portion 14 when the center valve seat 20 is installed, thereby facilitating installation, especially during maintenance. In some special installation positions, the center valve seat 20 can be fixed in the groove portion 14 to greatly reduce the maintenance and installation time; 2. By adding marks on the valve core 50, the action of the valve core 50 can be more quickly observed, thereby improving the maintenance efficiency; 3. The through hole 201 can also be in the form of a tool to help install the center valve seat 20, and the pressure of the center valve seat 20 on the second sealing gasket 21 can also be quickly adjusted without opening the pressure relief valve 900.

[0072] Further, the valve body 10 is further provided with a discharge port 105 corresponding to the feed port 104, the discharge port 105 also communicates with the second cavity section 102, in one application mode, the medium enters the second cavity section 102 from the feed port 104, and flows out from the discharge port 105 to be connected to the spraying system.

[0073] It can be understood that, also, as in the embodiment, the discharge port 105 is provided with a plug 70 to block the discharge port 105, and the feed port 104 is connected to the spraying system to set the pressure relief return valve 900.

[0074] The above is only the embodiment of the present application, and does not limit the patent scope of the present application, any equivalent structure or equivalent process transformation using the content of the present application specification and drawings, or directly or indirectly applied to other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A spraying system, characterized in that, The spraying system includes an air source, a spraying device, a pressure relief and return valve, and a nozzle. The spraying device includes an inlet and an outlet, wherein the inlet is connected to the air source pipeline, the outlet is connected to the feed inlet pipeline, the air source is also connected to the air inlet pipeline, and the nozzle pipeline is connected to the outlet or to the pipeline between the outlet and the pressure relief and return valve. The pressure relief and return valve includes a valve body and end caps and pressure relief pipes disposed on both sides of the valve body. The valve body includes a cavity and a valve core passing through the cavity. The cavity includes a first cavity section facing the end cap, a second cavity section facing the pressure relief pipe, and a third cavity section connecting the first cavity section and the second cavity section. The cavity also includes an air inlet communicating with the first cavity section and a feed inlet communicating with the second cavity section. A slide seat connected to the valve core is also provided in the first cavity section, and an isolation component is also provided in the third cavity section to isolate the first cavity section from the second cavity section. The end cap includes an accommodating space; The pressure relief fitting includes a connection hole and a pressure relief hole communicating with the second cavity section; The valve core includes a head end with a movable closed or open connection hole. A spring for applying tension to the slide is provided in the accommodating space. The valve body also includes a groove. The isolation assembly includes a central valve seat with a through hole corresponding to the groove. The through hole passes through the central valve seat, and at least a portion of the valve core can be seen through the through hole.

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