Device for testing stress distribution of sealing pair of control valve

Abstract

The utility model discloses a device for testing stress distribution of a sealing pair of a control valve, and belongs to the field of valve performance testing. The device comprises a test bench. The fluid supply assembly comprises a water tank, a water inlet pipe, a water pump and a water outlet pipe, the water inlet end of the water inlet pipe communicates with the water tank, and the water pump is installed at the water outlet end of the water inlet pipe. The pressure regulating assembly is mounted on the water outlet pipe; the to-be-tested control valve is mounted at the water outlet end of the water outlet pipe; the transparent protection plate is arranged on the test bench corresponding to the water outlet end of the control valve to be tested; and the DIC image acquisition assembly is mounted on the test board on one side, far away from the to-be-tested control valve, of the transparent protection plate, and an acquisition end of the DIC image acquisition assembly is arranged corresponding to the to-be-tested control valve. According to the utility model, the complex working conditions of the control valve to be detected are simulated through the fluid supply assembly, and the DIC image acquisition assembly is used for high-precision image acquisition processing, so that the detection precision is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to valve performance test technical field more specifically relates to a device for testing control valve sealing pair stress distribution. BACKGROUND

[0002] High-end control valve serves many special fields, and its application range is wide, including ultrahigh pressure, ultrahigh temperature pipe network system, nuclear island and conventional island safety system, power unit of aeroengine, environment control and life maintenance system of space station and submarine diving and equalization system etc.. These fields put forward extremely strict reliability requirements on the design of sealing pair of control valve. Compared with traditional mechanical seal, the sealing pair of high-end control valve faces the test of extreme working conditions such as high temperature, high pressure difference, strong corrosion and wear, which can easily cause a series of complex problems such as cavitation, erosion, corrosion, thermal deformation, blockage, indentation and scratch. In the design process of control valve sealing pair, the uniformity of sealing pair stress distribution is one of the key design considerations, which directly affects the sealing performance of control valve and the safety of system.

[0003] The performance test of the existing control valve is generally divided into sealing pair performance test and pressure uniformity test. The sealing pair performance test is used to detect the performance state of the sealing pair under the working state, so as to ensure that the sealing pair can effectively realize the sealing state. For example, a simple end face dynamic sealing pair sealing performance and friction state test device is disclosed in Chinese patent CN112197906A, which comprises an upper flange and a lower flange, wherein the upper flange is provided with a mounting hole in the middle, the lower surface is provided with a recessed cavity, and the two sides are respectively clamped into the inner metal sliding ring and the outer metal sliding ring. The cross section of the lower flange is in the shape of a "convex" character, and the upper part is assembled with the mounting hole of the upper flange through the outer circumferential surface. Although the device can realize the isolation of the medium in the rotating pair cavity and the outside world, ensure the demand of good sealing performance and small friction torque, but the method still has the following shortcomings: (1) mainly for the detection of sealing performance of control valve sealing pair, cannot detect the structural defects affecting the sealing performance, lacks theoretical verification and guidance design for specific parameters needing improvement; (2) only for valve performance test under specific working conditions and single variable, cannot simulate other working conditions of valve, and has difference with actual application of valve.

[0004] The pressure uniformity test test is used for detecting the uniformity of a pressure module or unit in a direct or indirect pressure state, so as to ensure the performance and service life of the structure in the pressure state; for example, a detection device for pressure uniformity of a chip mounter is disclosed in Chinese Patent No. CN206223340U, which comprises a support seat, a groove for placing pressure-sensitive paper is arranged on the support seat; the pressure-sensitive paper is placed in the groove on the support seat, and is used for observing the indentation morphology of the pressure head of the chip mounter; a pressure-sensitive paper pressing device is arranged above the pressure-sensitive paper, and plays a role of fixing and keeping the pressure-sensitive paper flat; a leveling device is arranged on the support seat, and is used for measuring the level of the support seat; a horizontal adjustment device is arranged at the bottom of the support seat, and is used for adjusting the level of the support seat; a chip mounter pressure head is arranged above the support seat, and is used for indentation test on the pressure-sensitive paper placed in the groove of the support seat. Although the device can detect the indentation by the pressure-sensitive paper to realize rapid detection of pressure uniformity, the method still has the following disadvantages: (1) the experimental data of the valve under complex service conditions may not be accurately collected, analyzed and processed, resulting in inaccurate detection of the contact pressure uniformity of the sealing pair of the control valve, and the performance of the control valve cannot be evaluated more comprehensively; (2) the device may have limitations in measurement accuracy, so that small pressure differences cannot be accurately captured, thereby affecting the reliability of the detection result.

[0005] Therefore, how to provide a test device capable of accurately measuring the stress distribution uniformity of the sealing valve plate of the control valve under complex working conditions is a technical problem that those skilled in the art urgently need to solve. Practical new type content

[0006] Therefore, the device for testing the stress distribution of the sealing pair of the control valve is provided to at least solve the problem that the stress distribution of the sealing valve plate under complex working conditions cannot be accurately tested in the prior art.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] A device for testing the stress distribution of the sealing pair of a control valve, the control valve to be tested comprising a valve body, a driving part, a rotating shaft and a sealing valve plate, a flow channel is formed in the valve body, the driving part is fixed to the outer wall of the valve body, the rotating shaft is rotatably connected to the inner wall of the flow channel perpendicular to the flow direction of the flow channel, and is in transmission connection with the output end of the driving part, the sealing valve plate is fixed with the rotating shaft, and the surface thereof is coated with DIC speckle paint, comprising:

[0009] A test table;

[0010] A fluid supply assembly, which comprises a water tank, a water inlet pipe, a water pump and a water outlet pipe, the water tank is arranged below the test table, the water inlet end of the water inlet pipe is communicated with the water tank, the water pump is installed at the water outlet end of the water inlet pipe, the water inlet end of the water outlet pipe is communicated with the water outlet end of the water pump, the valve body is installed at the water outlet end of the water outlet pipe and the flow channel is communicated with the water outlet end of the water outlet pipe;

[0011] A pressure regulating assembly is installed on the water outlet pipe;

[0012] A transparent protective plate is installed on the test table corresponding to the water outlet end of the valve body;

[0013] A DIC image acquisition assembly is installed on the test table top away from the valve body side of the transparent protective plate and its acquisition end is arranged corresponding to the sealing valve plate to acquire the deformation image of the sealing valve plate.

[0014] The utility model discloses a beneficial effect can be realized: through fluid supply assembly simulation measured control valve work complex working condition condition, and the DIC speckle paint is applied on the sealing valve plate as the sealing pair, thereby utilizing DIC image acquisition assembly to acquire sealing valve plate image, thereby be favorable to the deformation condition of each point of sealing valve plate, realize the accurate analysis of stress distribution on sealing valve plate, improve the accuracy of detection.

[0015] Preferably, the pressure regulating assembly comprises a pressure stabilizing tank, a pressure gauge and a pressure relief valve, which are installed on the water outlet pipe between the water pump and the valve body in sequence.

[0016] Preferably, the sealing valve plate is a D printing integrated structure.

[0017] Preferably, the transparent protective plate is a U-shaped plate, and the open end thereof is arranged opposite to the valve body.

[0018] Preferably, the transparent protective plate is a high-transparency tempered glass plate.

[0019] Preferably, the DIC image acquisition assembly comprises a high-speed camera, an image processor and a display screen, the high-speed camera is installed on the test table top corresponding to the side of the transparent protective plate away from the valve body, and the acquisition end of the high-speed camera is arranged corresponding to the sealing valve plate; the image processor is electrically connected with the high-speed camera, and the display screen is electrically connected with the image processor.

[0020] Preferably, the high-speed camera is provided with a plurality of slidingly installed on the slide rail arranged perpendicular to the water outlet direction of the water outlet pipe, and the acquisition end of the high-speed camera is arranged corresponding to the sealing valve plate.

[0021] Preferably, the DIC image acquisition assembly further comprises a high-speed camera angle adjusting assembly, the high-speed camera angle adjusting assembly comprising a base, a spherical rotating block, a support seat and a locking bolt, the base being slidingly connected to the slide rail, and a spherical rotating groove being formed in the top of the base, the spherical rotating block being rotatably connected in the spherical rotating groove, the support seat being fixed on the top of the spherical rotating block, the high-speed camera being mounted on the top of the support seat, and the locking bolt extending through the side wall of the base into the spherical rotating groove and abutting against the spherical rotating block to lock the spherical rotating block.

[0022] Preferably, the DIC image acquisition assembly further comprises a light supplementing lamp, the light supplementing lamp being mounted on the test table corresponding to the sealing valve plate.

[0023] Preferably, a backflow assembly is further provided, the backflow assembly comprising a backflow pipe and a backflow valve, the water inlet end of the backflow pipe being communicated with the water outlet pipe, and the water outlet end being communicated with the water tank, and the backflow valve being mounted on the backflow pipe.

[0024] Compared with the prior art, the technical scheme can provide a device for testing stress distribution of a sealing pair of a control valve, simulate complex working conditions through a fluid supply assembly, and perform high-precision image acquisition and processing through a DIC image acquisition assembly, thereby improving detection precision, ensuring accuracy of test data and actual applicability of results, effectively verifying optimization effect of a sealing valve plate, and identifying structural defects of a butterfly plate with insufficient sealing performance, so that sealing performance and design optimization level of the sealing valve plate of the control valve are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the drawings needed to be used in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0026] Figure 1 A perspective structural schematic view of the device for testing stress distribution of a sealing pair of a control valve is provided.

[0027] Figure 2 A front view structural schematic view of the device for testing stress distribution of a sealing pair of a control valve is provided.

[0028] Figure 3 A perspective structural schematic view of the control valve is provided.

[0029] Figure 4 The utility model provides a high -speed camera and the structural diagram of slide rail.

[0030] In the drawing: 1, test platform, 11, slide rail, 2, fluid supply assembly, 21, water tank, 22, water inlet pipe, 23, water pump, 24, water outlet pipe, 3, pressure regulating assembly, 31, pressure stabilizing tank, 32, pressure gauge, 33, pressure relief valve, 4, control valve to be measured, 41, valve body, 42, drive part, 43, rotating shaft, 44, sealing valve plate, 5, transparent protective plate, 6, image acquisition assembly, 61, high -speed camera, 62, image processor, 63, display screen, 64, high -speed camera angle adjusting assembly, 641, base, 642, spherical rotating block, 643, support seat, 644, locking bolt, 65, fill light, 7, backflow assembly, 71, backflow pipe, 72, backflow valve. DETAILED DESCRIPTION

[0031] The technical scheme in the embodiments of the utility model will be described clearly and completely below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the utility model.

[0032] In the description of the utility model, it is understood that the orientation or position relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is the orientation or position relationship shown in the drawings, and is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the utility model.

[0033] In the utility model, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, it can be the communication inside two elements or the interaction relationship of two elements. For those skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0034] Please refer to Figure 3The control valve to be tested in the embodiment is a three-eccentric butterfly valve, and a model of the original three-eccentric butterfly valve is used in the experiment, including a valve body 41, a driving part 42, a rotating shaft 43 and a sealing valve plate 44.

[0035] Referring to Figure 1 、 Figures 2-4 The utility model discloses an apparatus for testing control valve sealing pair stress distribution, include: test board 1, fluid supply component 2, pressure regulating component 3, transparent protection board 5 and DIC image acquisition component 6.

[0036] Test board 1 includes a plurality of columns and a bottom plate and a top plate installed on the columns.

[0037] Fluid supply component 2 includes a water tank 21, a water inlet pipe 22, a water pump 23 and a water outlet pipe 24, the water tank 21 is placed on the ground, the water inlet end of the water inlet pipe 22 is communicated with the water tank 21, the water pump 23 is a constant pressure variable frequency pump, a constant pressure variable frequency pump with a model of CDLZN12-120-7.5Kw can be used, the water pump 23 is fixed on the bottom plate and connected with the water outlet end of the water inlet pipe 22, the water inlet end of the water outlet pipe 24 is communicated with the water outlet end of the water pump 23, the water outlet end passes through the top plate upwards and extends to the side away from the water tank 21, and is fixed on the top plate by buckling;

[0038] Pressure regulating component 3 is installed on the water outlet pipe 24 for adjusting water flow pressure; the valve body 41 is installed on the water outlet end of the water outlet pipe 24; the top plate is recessed downwards at the valve body 41 to make the water flowing out of the control valve 4 to be tested to flow out smoothly, avoiding the pollution of other equipment on the table surface; the transparent protection plate 5 is installed on the recessed part of the test board 1 corresponding to the water outlet end of the valve body 41 to prevent water from splashing on the DIC image acquisition component 6; the sealing valve plate surface is coated with DIC speckle paint, and the DIC image acquisition component 6 is installed on the test board 1 away from the valve body 41 side of the transparent protection plate 5, and the acquisition end thereof is arranged corresponding to the sealing valve plate 44 to collect the deformation conditions of each point on the surface of the sealing valve plate 44 through the DIC speckle paint.

[0039] Pressure regulating component 3 includes a pressure stabilizing tank 31, a pressure gauge 32 and a pressure relief valve 33, the pressure stabilizing tank 31, the pressure gauge 32 and the pressure relief valve 33 are installed on the water outlet pipe 24 between the water pump 23 and the test valve in sequence, so as to adjust the water flow pressure and ensure the pressure stability, to detect the stress conditions of the control valve 4 to be tested under different pressures.

[0040] The sealing valve plate 44 used in the test is a 3D printing integrated structure. The original sealing valve plate 44 of the three-eccentric butterfly valve model includes a butterfly plate, a sealing ring and a pressing plate, which are connected by bolts. The experimental three-eccentric butterfly valve is printed as a whole during printing, solving the problem of difficult assembly of the three parts and facilitating the assembly and connection between the sealing valve plate 44 and the valve body 41.

[0041] The transparent protective plate 5 is a U-shaped plate, and its open end is arranged opposite to the valve body 41. It plays a multi-directional splash-proof role and prevents the liquid leaked from the test valve from splashing and polluting the DIC image acquisition assembly 6.

[0042] The transparent protective plate 5 is a high-transparency tempered glass plate, which has high strength and strong perspective. It can play a protective role on the DIC image acquisition assembly 6 without affecting the image acquisition effect.

[0043] The DIC image acquisition assembly 6 includes a high-speed camera 61, an image processor 62 and a display screen 63. The high-speed camera 61 is fixed on the top of the test bench 1 corresponding to the side of the transparent protective plate 5 away from the valve body 41, and the collection end of the high-speed camera 61 is arranged corresponding to the sealing valve plate 44. The image processor 62 is electrically connected to the high-speed camera 61, and the display screen 63 is electrically connected to the image processor 62. The high-speed camera 61 is used to take pictures of the sealing valve plate 44, and the taken pictures are transmitted to the image processor 62. The image processor 62 processes and analyzes the received data to form a deformation and strain cloud image displayed on the display screen 63.

[0044] A plurality of high-speed cameras 61 are provided. The test bench 1 has a plurality of slide rails 11 arranged along the water outlet direction of the water outlet pipe 24. The plurality of high-speed cameras 61 are slidably installed on the slide rails, and the collection end of the high-speed camera 61 is arranged corresponding to the sealing valve plate 44.

[0045] The DIC image acquisition assembly 6 further includes a high-speed camera angle adjusting assembly 64. The high-speed camera angle adjusting assembly 64 includes a base 641, a spherical rotating block 642, a support seat 643 and a locking bolt 644. The base 641 is slidably connected to the slide rail 11, and a spherical rotating groove is formed in the top of the base 641. The spherical rotating block 642 is rotatably connected in the spherical rotating groove. The support seat 643 is fixed on the top of the spherical rotating block 642. The high-speed camera is installed on the top of the support seat 643. The locking bolt 644 extends through the side wall of the base 641 into the spherical rotating groove and abuts with the spherical rotating block 642 to lock the spherical rotating block 642. The inclination angle of the high-speed camera 61 can be adjusted by rotating the spherical rotating block 642, and the height of the camera can be adjusted to correspond to the sealing valve plate 44, ensuring the image acquisition quality.

[0046] The DIC image acquisition assembly 6 further comprises a light supplement lamp 65 which is installed on the test table 1 through a movable arm and corresponds to the sealing valve plate 44 to supplement light for the sealing valve plate 44 and enhance the accuracy when the high-speed camera 61 is shooting.

[0047] A backflow assembly 7 is further provided, which comprises a backflow pipe 71 and a backflow valve 72. The water inlet end of the backflow pipe 71 is communicated with the water outlet pipe 24, and the water outlet end is communicated with the water tank 21. The backflow valve 72 is installed on the backflow pipe 71. After the test is completed, the backflow valve 72 is opened, and the water flows back to the water tank 21 through the backflow pipe 71, so as to be reused, save energy and be environment-friendly.

[0048] The embodiment further provides a control valve sealing valve plate stress distribution test method, which comprises the following steps:

[0049] 1. Spraying DIC speckle paint on the surface of the sealing valve plate 44, and assembling and connecting each structure stably;

[0050] 2. Turning on the variable frequency water pump 23, adjusting the water flow pressure according to the test needs, and maintaining the water pressure in a stable state under the action of the pressure stabilizing tank 31;

[0051] 3. Turning on the high-speed camera 61 to shoot the sealing valve plate 44 through the transparent protective plate 5, and transmitting the shot picture to the image processor 62. The image processor 62 processes and analyzes the received data to form a deformation and strain cloud picture on the display screen 63. According to the image display structure, the stress distribution of the sealing valve plate 44 on the sealing valve plate 44 can be understood;

[0052] 4. Changing the water flow pressure, shooting the image again after the pressure is stable, so that the maximum and minimum contact stress positions can be found according to the stress state of the valve under various pressure conditions, and the design of the sealing valve plate 44 is guided according to the results.

[0053] The device can simulate complex working conditions to improve the authenticity of the sealing valve plate stress distribution test. The DIC image acquisition assembly can accurately detect the stress distribution of each part of the sealing valve plate, judge whether the stress distribution of the sealing valve plate is uniform, and find the structure defect position of the sealing valve plate in the test, so as to provide a reference for designing the sealing valve plate and optimization. At the same time, it can provide guidance for improving the sealing performance of the valve, reducing the cost and weight, and other multi-objective optimization. The best structure and optimal size of the three eccentric butterfly valve disc are found through related algorithms and other methods.

[0054] The various embodiments described in this specification are presented by way of example, and each embodiment is presented for the purpose of conveying the novelty and inventive aspects of the present patent application. For the embodiments disclosed, because they correspond to the methods disclosed in the embodiments, they are described more simply, and the relevant parts are referred to the method part description.

[0055] The above description of disclosed embodiments enables one of ordinary skill in the art to make and use the patent application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the patent application. Thus, the present patent application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus for testing stress distribution of a sealing pair of a control valve, the control valve to be tested comprising a valve body (41), a driving part (42), a rotating shaft (43) and a sealing valve plate (44), a flow passage being formed in the valve body (41), the driving part (42) being fixed to an outer sidewall of the valve body (41), the rotating shaft (43) being rotatably connected to an inner sidewall of the flow passage in a direction of flow of the flow passage and being in driving connection with an output end of the driving part (42), the sealing valve plate (44) being fixed to the rotating shaft (43) and having a surface coated with DIC speckle paint, characterized in that, The utility model relates to a test platform for testing the sealing performance of valve plate, comprising: a test platform (1); a fluid supply assembly (2) comprising a water tank (21), a water inlet pipe (22), a water pump (23) and a water outlet pipe (24), the water tank (21) is placed below the test platform (1), the water inlet end of the water inlet pipe (22) is communicated with the water tank (21), the water pump (23) is installed at the water outlet end of the water inlet pipe (22), the water inlet end of the water outlet pipe (24) is communicated with the water outlet end of the water pump (23), the valve body (41) is installed at the water outlet end of the water outlet pipe and the flow channel is communicated with the water outlet end of the water outlet pipe (24); a pressure regulating assembly (3) installed on the water outlet pipe (24); a transparent protective plate (5) installed on the test platform (1) corresponding to the water outlet end of the valve body (41); a DIC image acquisition assembly (6) installed on the test platform (1) on the side of the transparent protective plate (5) away from the valve body (41) and arranged corresponding to the sealing valve plate (44) at the acquisition end.

2. An apparatus for testing stress distribution of a seal pair of a control valve according to claim 1, characterized in that, The pressure regulating assembly (3) comprises a pressure stabilizing tank (31), a pressure gauge (32) and a pressure relief valve (33), which are installed in sequence on the water outlet pipe (24) between the water pump (23) and the valve body (41).

3. An apparatus for testing stress distribution of a seal pair of a control valve according to claim 1, characterized in that, The sealing valve plate (44) is a 3D printed integrated structure.

4. An apparatus for testing stress distribution of a seal pair of a control valve according to claim 1, characterized in that, The transparent protective plate (5) is a U-shaped plate, and the open end is arranged opposite to the valve body (41).

5. An apparatus for testing stress distribution of a seal pair of a control valve according to claim 1, characterized in that, The transparent protective plate (5) is a high-transparency tempered glass plate.

6. An apparatus for testing stress distribution of a seal pair of a control valve according to claim 1, characterized by The DIC image acquisition assembly (6) comprises a high-speed camera (61), an image processor (62) and a display screen (63), the high-speed camera (61) is installed on the top of the test platform (1) corresponding to the side of the transparent protective plate (5) away from the valve body (41), and the acquisition end is arranged corresponding to the sealing valve plate (44); the image processor (62) is electrically connected with the high-speed camera (61), and the display screen (63) is electrically connected with the image processor (62).

7. An apparatus for testing stress distribution of a seal pair of a control valve according to claim 6, characterized in that, The high-speed camera (61) is provided with a plurality of sliding rails (11) arranged vertically to the water outlet direction of the water outlet pipe (24) on the top of the test platform (1), and a plurality of high-speed cameras (61) are slidingly installed on the sliding rails (11), so that the acquisition end is arranged corresponding to the sealing valve plate (44).

8. An apparatus for testing stress distribution of a seal pair of a control valve according to claim 7, characterized in that, The DIC image acquisition assembly (6) further comprises a high-speed camera angle adjusting assembly (64), the high-speed camera angle adjusting assembly (64) comprises a base (641), a spherical rotating block (642), a supporting seat (643) and a locking bolt (644), the base (641) is slidably connected on the slide rail (11), and a spherical rotating groove is formed in the top of the base (641), the spherical rotating block (642) is rotatably connected in the spherical rotating groove, the supporting seat (643) is fixed on the top of the spherical rotating block (642), the high-speed camera is installed on the top of the supporting seat (643), and the locking bolt (644) extends into the spherical rotating groove through the side wall of the base (641) and abuts against the spherical rotating block (642) to lock the spherical rotating block (642).

9. An apparatus for testing stress distribution of a seal pair of a control valve according to claim 6, wherein The DIC image acquisition assembly (6) further comprises a light supplement lamp (65), and the light supplement lamp (65) is installed on the test table (1) corresponding to the sealed valve plate (44).

10. An apparatus for testing stress distribution of a seal pair of a control valve according to any one of claims 1 to 9, characterized in that, A backflow assembly (7) is further arranged, and the backflow assembly (7) comprises a backflow pipe (71) and a backflow valve (72), the water inlet end of the backflow pipe (71) is communicated with the water outlet pipe (24), the water outlet end is communicated with the water tank (21), and the backflow valve (72) is installed on the backflow pipe (71).

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