A high-temperature liquid metal circulating pump with noise reduction

Abstract

The application relates to the technical field of circulating pumps, in particular to a high-temperature liquid metal circulating pump with noise reduction, which comprises a liquid discharge pipe, a flow guide pipe and a liquid inlet pipe, the flow guide pipe is fixedly installed in the interiors of the liquid discharge pipe and the liquid inlet pipe, a flow guide frame is fixedly installed in the interior of the flow guide pipe, and a rotating shaft is rotatably installed on the inner side of the flow guide frame. The vibration of the rotating cylinder and the flow guide cylinder reduces the turbulence generated in the liquid metal flow process, effectively reduces the operation noise, the longitudinal vibration can offset the shaking and circumferential vibration generated in the circulating process, the stability of equipment operation is further improved, the vibration of the flow guide cylinder makes the bubbles gradually gather in the gas collection groove, the amount of residual bubbles in the liquid metal is reduced, the cavitation of the bubbles on the impeller and the noise in the rotating process of the impeller are reduced, the bubbles are separated from the flow channel of the liquid metal circulation through the conveying of the spiral groove, the interference of the bubbles on the stability of the circulating system is further reduced, and the noise reduction effect is improved.

Description

Technical Field

[0001] This invention relates to the field of circulating pump technology, and in particular to a noise-reducing high-temperature liquid metal circulating pump. Background Technology

[0002] During the continuous operation of a high-temperature liquid metal circulation system, the fluctuation of oxygen concentration in the liquid lead-bismuth alloy under high-temperature, high-density liquid metal flow conditions causes bubbles to continuously accumulate inside the system. These bubbles often originate from the precipitation of dissolved gases in the liquid metal, cavitation during the flow process, or the infiltration of argon gas from the external system. The accumulated bubbles lead to a significant decrease in fluid dynamics performance, not only increasing flow resistance but also causing abnormal pressure fluctuations and local cavitation. In addition, high-frequency noise is continuously generated during the high-speed circulation of liquid metal. This noise originates from cavitation collapse and fluid turbulence, as well as being affected by pump mechanical vibration. This not only causes potential damage to the equipment itself but also has a long-term adverse impact on the operating environment. As the bubbles circulate with the liquid metal, they rupture rapidly at the impeller, generating intense microjet flow, which leads to pitting and fatigue damage on the impeller surface. Long-term operation will significantly reduce the mechanical strength and service life of the impeller. At the same time, the presence of bubbles also interferes with the stable flow of the fluid, causing flow pulsation and a reduction in energy transfer efficiency, thereby weakening the operational stability of the entire circulation system and even affecting the long-term reliability and lifespan of the system. Summary of the Invention

[0003] The purpose of this invention is to solve the problems in the background art by proposing a noise-reducing high-temperature liquid metal circulating pump.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A noise-reducing high-temperature liquid metal circulating pump includes a discharge pipe, a guide pipe, and an inlet pipe. The guide pipe is fixedly installed inside the discharge pipe and the inlet pipe. A guide frame is fixedly installed inside the guide pipe. A rotating shaft is rotatably installed on the inner side of the guide frame. A rotating cylinder is slidably fitted on the outer peripheral wall of the rotating shaft. A settling cavity is opened on the inner side of the guide frame. The rotating cylinder is movably installed inside the settling cavity. A guide cylinder is slidably installed inside the inlet pipe. The rotating cylinder is rotatably installed inside the guide cylinder. An impeller is fixedly installed at the bottom of the rotating shaft. A guide wheel is fixedly fitted on the side wall of the rotating shaft. The guide wheel is located between the impeller and the guide cylinder. A drive motor is fixedly installed at the top of the guide frame. The drive motor is located outside the discharge pipe. The output shaft of the drive motor is fixedly connected to the rotating shaft.

[0006] Preferably, the side wall of the rotating cylinder is integrally formed with a sliding rod, the inner side of the flow guide frame is provided with a corrugated groove, the sliding rod is slidably installed inside the corrugated groove, and a plurality of evenly distributed flow guide plates are welded to the inner side of the flow guide frame.

[0007] Preferably, the side wall of the rotating cylinder is provided with a plurality of evenly distributed spiral grooves, and the interior of the rotating cylinder is provided with a plurality of evenly distributed liquid inlet holes. The liquid inlet holes and the spiral grooves correspond one to one and are interconnected. The liquid inlet holes are located inside the settling chamber.

[0008] Preferably, a plurality of evenly distributed guide vanes are welded to the inner side of the guide tube, and air guide grooves are provided on the side walls of both sides of the guide vanes. An air collection groove is provided on the top of the guide vanes. The air guide grooves and the air collection grooves are connected, and the air collection grooves are located below the spiral grooves.

[0009] Preferably, the rotating cylinder has an exhaust port three inside, which is connected to the inner side of the settling chamber and the guide frame respectively. Piston ring one and piston ring two are slidably installed inside the settling chamber. Piston ring one is rotatably fitted on the outer side of the rotating cylinder, and piston ring two is movably fitted on the outer side of the rotating cylinder. Piston ring one is located between the liquid inlet and the exhaust port three, and piston ring two is located below piston ring one.

[0010] Preferably, the bottom of the piston ring one is integrally formed with a sealing plug, and the side wall of the piston ring two is provided with a sealing hole. The sealing plug is slidably inserted into the inside of the sealing hole, and the inside of the piston ring two is hollow.

[0011] Preferably, the piston ring 1 has a vent hole 4 on its side wall, and a one-way valve 1 is provided on the top of the vent hole 4. The drain pipe and the guide frame have vent holes 1 and 2 on their side walls, respectively, and the vent holes 1 and 2 correspond to each other.

[0012] Preferably, the bottom of the settling chamber is provided with a drain hole, and the end of the drain hole connected to the guide pipe is inclined upward. The drain hole is located below the piston ring two. The drain hole is provided with a one-way pressure valve inside, and the inlet hole is provided with a one-way valve two inside.

[0013] Compared with existing technologies, the beneficial effects of this invention are as follows:

[0014] 1. During the circulation of high-temperature liquid metal, the rotating drum drives the guide drum to move up and down rapidly, causing the rotating drum and the guide drum to vibrate longitudinally. The vibration of the rotating drum and the guide drum reduces the turbulence generated during the flow of liquid metal, effectively reducing operating noise. At the same time, the longitudinal vibration can cancel out the swaying and circumferential vibration generated during the circulation process, further improving the stability of equipment operation.

[0015] 2. The vibration of the guide tube causes the bubbles to gradually converge in the gas collection tank, reducing the amount of residual bubbles in the liquid metal, reducing cavitation of the impeller and noise during impeller rotation, and improving the uniformity of liquid metal flow and heat transfer efficiency.

[0016] 3. During the rotation of the rotating cylinder, the bubbles gathered in the gas collecting groove are drawn into the interior of the spiral groove, which in turn transports the bubbles and liquid metal inside to the interior of the settling chamber for settling. Through the transport of the spiral groove, the bubbles are removed from the flow channel of the liquid metal circulation, further reducing the interference of bubbles on the stability of the circulation system and improving the noise reduction effect. Attached Figure Description

[0017] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0018] Figure 2 This is a cross-sectional view of the overall structure of the present invention;

[0019] Figure 3 For the present invention Figure 2 Enlarged schematic diagram of the structure at point A;

[0020] Figure 4 This is a schematic diagram of the structure of the present invention after removing the drain pipe, guide pipe and inlet pipe;

[0021] Figure 5 This is a cross-sectional view of the flow guide frame in this invention;

[0022] Figure 6 This is a schematic diagram of the rotating cylinder in this invention;

[0023] Figure 7 This is a schematic diagram of the structure of piston ring one and piston ring two in this invention;

[0024] Figure 8 This is a cross-sectional view of the flow guide tube in this invention;

[0025] Figure 9 For the present invention Figure 8 Enlarged schematic diagram of the structure at point B.

[0026] In the diagram: 1. Drain pipe; 11. Guide pipe; 12. Inlet pipe; 13. Exhaust port one; 14. Drive motor; 141. Rotating shaft; 142. Guide wheel; 143. Impeller; 21. Guide frame; 211. Exhaust port two; 212. Guide vane one; 213. Settling chamber; 214. Drain hole; 215. One-way pressure valve; 216. Corrugated groove; 22. Rotating cylinder; 221. Slide rod; 222. Spiral groove; 223. Inlet hole; 224. One-way valve two; 225. Exhaust port three; 23. Guide cylinder; 231. Guide vane two; 232. Air guide groove; 233. Air collection groove; 311. Piston ring one; 312. One-way valve one; 313. Exhaust port four; 314. Sealing plug; 315. Piston ring two; 316. Sealing hole. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0029] Reference Figure 1 - Figure 9 As shown, a noise-reducing high-temperature liquid metal circulating pump includes a drain pipe 1, a guide pipe 11, and an inlet pipe 12. The guide pipe 11 is fixedly installed inside the drain pipe 1 and the inlet pipe 12. A guide frame 21 is fixedly installed inside the guide pipe 11. A rotating shaft 141 is rotatably installed on the inner side of the guide frame 21. A rotating cylinder 22 is slidably fitted on the outer peripheral wall of the rotating shaft 141. A settling cavity 213 is opened on the inner side of the guide frame 21, and the rotating cylinder 22 is movably installed on the inner side of the settling cavity 213. A guide tube 23 is slidably installed inside the inlet pipe 12. A rotating cylinder 22 is rotatably installed inside the guide tube 23. An impeller 143 is fixedly installed at the bottom of the rotating shaft 141. A guide wheel 142 is fixedly fitted on the side wall of the rotating shaft 141. The guide wheel 142 is located between the impeller 143 and the guide tube 23. A drive motor 14 is fixedly installed at the top of the guide frame 21. The drive motor 14 is located outside the drain pipe 1. The output shaft of the drive motor 14 is fixedly connected to the rotating shaft 141.

[0030] like Figure 2 , Figure 5 and Figure 6As shown, the side wall of the rotating cylinder 22 is integrally formed with a sliding rod 221, and the inner side of the flow guide frame 21 is provided with a corrugated groove 216. The sliding rod 221 is slidably installed inside the corrugated groove 216, and a number of evenly distributed flow guide plates 212 are welded to the inner side of the flow guide frame 21.

[0031] During the circulation of high-temperature liquid metal, the drive motor 14 drives the rotating shaft 141 to rotate. The rotating shaft 141 drives the impeller 143, the guide wheel 142, and the rotating cylinder 22 to rotate. The impeller 143 and the guide wheel 142 drive the high-temperature liquid metal to circulate. The rotating cylinder 22 moves up and down rapidly through the slide rod 221 and the corrugated groove 216. The guide cylinder 23 follows the rotating cylinder 22 and moves up and down rapidly, causing the rotating cylinder 22 and the guide cylinder 23 to vibrate longitudinally. The vibration of the rotating cylinder 22 and the guide cylinder 23 reduces the turbulence generated during the flow of liquid metal, effectively reducing operating noise. At the same time, the longitudinal vibration can cancel out the shaking and circumferential vibration generated during the circulation process, further improving the stability of the equipment operation.

[0032] like Figure 3 , Figure 4 and Figure 6 As shown, the side wall of the rotating cylinder 22 is provided with several evenly distributed spiral grooves 222, and the interior of the rotating cylinder 22 is provided with several evenly distributed liquid inlet holes 223. The liquid inlet holes 223 and the spiral grooves 222 correspond one to one and are interconnected. The liquid inlet holes 223 are located inside the stationary cavity 213.

[0033] like Figure 2 , Figure 4 , Figure 8 and Figure 9 As shown, several evenly distributed guide vanes 231 are welded to the inner side of the guide tube 23. Air guide grooves 232 are provided on the side walls of both sides of the guide vanes 231. An air collection groove 233 is provided on the top of the guide vanes 231. The air guide grooves 232 and the air collection grooves 233 are connected. The air collection grooves 233 are located below the spiral grooves 222.

[0034] During the longitudinal vibration of the guide tube 23, the guide tube 23 drives the guide vane 231 to vibrate, causing the bubbles in the liquid metal to move to the inside of the air guide groove 232 with slight disturbances caused by the vibration of the guide vane 231. The bubbles then gather in the air collection groove 233 along the air guide groove 232. Through the vibration of the guide tube 23, the bubbles gradually converge in the air collection groove 233, reducing the amount of residual bubbles in the liquid metal, reducing the cavitation of the impeller 143 by the bubbles and the noise during the rotation of the impeller 143, while improving the uniformity of the liquid metal flow and the heat transfer efficiency.

[0035] As the rotating cylinder 22 rotates along with the rotating shaft 141, it drives the spiral groove 222 to rotate, causing the bubbles gathered in the gas collecting groove 233 to be drawn into the interior of the spiral groove 222. The spiral groove 222 then transports the bubbles and liquid metal upwards, allowing them to enter the settling chamber 213 through the liquid inlet 223 for settling. Through the transport of the spiral groove 222, the bubbles are removed from the liquid metal circulation channel, further reducing the interference of bubbles on the stability of the circulation system and improving the noise reduction effect.

[0036] like Figure 2 , Figure 3 , Figure 6 and Figure 7 As shown, the rotating cylinder 22 has an exhaust port 3 225 inside. The exhaust port 3 225 is connected to the inner side of the settling chamber 213 and the guide frame 21 respectively. The settling chamber 213 has a piston ring 1 311 and a piston ring 2 315 slidably installed inside. The piston ring 1 311 is rotatably fitted on the outside of the rotating cylinder 22, and the piston ring 2 315 is movably fitted on the outside of the rotating cylinder 22. The piston ring 1 311 is located between the liquid inlet 223 and the exhaust port 3 225, and the piston ring 2 315 is located below the piston ring 1 311. The side wall of the piston ring 1 311 has an exhaust port 4 313, and the top of the exhaust port 4 313 is equipped with a one-way valve 1 312.

[0037] like Figure 3 and Figure 7 As shown, the bottom of piston ring 311 is integrally formed with a sealing plug 314, and the side wall of piston ring 315 is provided with a sealing hole 316. The sealing plug 314 is slidably inserted into the inside of the sealing hole 316, and the inside of piston ring 315 is hollow.

[0038] like Figure 2 , Figure 4 and Figure 5 As shown, the side walls of the drain pipe 1 and the guide frame 21 are respectively provided with vent hole 13 and vent hole 211, and vent hole 13 and vent hole 211 correspond to each other.

[0039] like Figure 3 and Figure 5 As shown, a drain hole 214 is provided at the bottom of the settling chamber 213. The end of the drain hole 214 connected to the guide pipe 11 is inclined upward. The drain hole 214 is located below the piston ring 315. A one-way pressure valve 215 is provided inside the drain hole 214. A one-way valve 224 is provided inside the inlet hole 223.

[0040] In this process, after the bubbles and liquid metal enter the settling chamber 213, piston ring 2 315 floats above the liquid metal. At this time, piston ring 2 315 is located between the bubbles and the liquid metal, and the bubbles are located between piston ring 2 315 and piston ring 1 311. During the up-and-down movement of the rotating cylinder 22, piston ring 1 311 moves up and down with the rotating cylinder 22. When the sealing plug 314 is inserted into the sealing hole 316, piston ring 1 311 continues to move downward and compresses the space between it and piston ring 2 315. At this time, the pressure between piston ring 1 311 and piston ring 2 315 is less than the set value of the one-way pressure valve 215, causing one-way valve 1 312 to open and one-way valve 224 and one-way pressure valve 215 to close. The bubbles between piston ring 1 311 and piston ring 2 315 are discharged into the guide frame 21 through exhaust hole 3 225. At this time, the bubbles are discharged through exhaust hole 1 13 and exhaust hole 2 12. After the air bubbles between piston ring 1 (311) and piston ring 2 (315) are expelled, piston ring 1 (311) drives piston ring 2 (315) to move downwards. At this time, one-way pressure valve 215 opens, allowing piston ring 2 (315) to discharge the liquid metal below through drain hole 214 into the liquid metal circulation channel. When piston ring 1 (311) moves upwards, one-way pressure valve 215 and one-way valve 1 (312) close, one-way valve 2 (224) opens, and piston ring 2 (315) stops moving. This allows piston ring 1 (311) to draw the air bubbles and liquid metal inside inlet hole 223 between piston ring 1 (311) and piston ring 2 (315). The above steps are repeated. Through the mutual movement between piston ring 1 (311) and piston ring 2 (315), the air bubbles and liquid metal inside the settling chamber 213 are completely separated, effectively preventing air bubbles from entering the liquid metal circulation channel, thereby ensuring the stability and safety of the liquid metal circulation process.

[0041] The working principle and usage of this invention are explained in detail below: During the circulation of high-temperature liquid metal, the drive motor 14 drives the impeller 143, guide wheel 142, and rotating cylinder 22 to rotate. The impeller 143 and guide wheel 142 drive the high-temperature liquid metal to circulate. During the rotation, the rotating cylinder 22 drives the guide cylinder 23 to move up and down rapidly, causing the rotating cylinder 22 and guide cylinder 23 to vibrate longitudinally. Through the vibration of the rotating cylinder 22 and guide cylinder 23, the turbulence generated during the flow of liquid metal is reduced, effectively reducing operating noise. At the same time, the longitudinal vibration can cancel out the swaying and circumferential vibration generated during the circulation process, further improving the stability of the equipment operation. During the process, bubbles in the liquid metal are slightly disturbed by the vibration of the guide vane 231 and move to the inside of the gas guide groove 232, and gather along the gas guide groove 232 towards the gas collection groove 233. Through the vibration of the guide cylinder 23, the bubbles gradually converge in the gas collection groove 233, reducing the amount of residual bubbles in the liquid metal, reducing cavitation of the impeller 143 and noise during impeller 143 rotation, and simultaneously improving the uniformity of liquid metal flow and heat transfer efficiency. During the rotation of the rotating cylinder 22, the rotating cylinder 22 drives the spiral groove 222 to rotate, causing the bubbles gathered in the gas collection groove 233 to be drawn into the interior of the spiral groove 222. The spiral groove 222 then transports the bubbles and liquid metal upwards, allowing them to pass through... The liquid enters the settling chamber 213 through the inlet hole 223 and settles there. The spiral groove 222 transports the bubbles away from the liquid metal circulation channel, further reducing their interference with the stability of the circulation system and improving noise reduction. After the bubbles and liquid metal enter the settling chamber 213, piston ring 2 315 floats above the liquid metal, positioned between the bubbles and the liquid metal. The bubbles are located between piston ring 2 315 and piston ring 1 311. As the rotating cylinder 22 moves up and down, piston ring 1 311 moves up and down with it. When the sealing plug 314 is inserted into the sealing hole 316, piston ring 1 311 compresses the space between itself and piston ring 2 315, causing... The air bubbles between piston ring 1 (311) and piston ring 2 (315) are expelled. After the air bubbles are expelled, piston ring 1 (311) drives piston ring 2 (315) to move downward, causing piston ring 2 (315) to discharge the liquid metal below into the circulation channel. When piston ring 1 (311) moves upward, piston ring 2 (315) stops moving, causing piston ring 1 (311) to draw the air bubbles and liquid metal inside the liquid inlet 223 into the space between piston ring 1 (311) and piston ring 2 (315). The above steps are repeated. Through the mutual movement between piston ring 1 (311) and piston ring 2 (315), the air bubbles and liquid metal inside the settling chamber 213 are completely separated, effectively preventing air bubbles from entering the liquid metal circulation channel, thereby ensuring the stability and safety of the liquid metal circulation process.

[0042] To further clarify, the aforementioned fixed connection should be interpreted broadly unless otherwise explicitly specified and limited. For example, it may be welding, gluing, or integral molding, or other conventional methods well known to those skilled in the art.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A noise-reducing high-temperature liquid metal circulating pump, comprising a drain pipe (1), a guide pipe (11), and an inlet pipe (12), characterized in that: The guide pipe (11) is fixedly installed inside the drain pipe (1) and the inlet pipe (12). A guide frame (21) is fixedly installed inside the guide pipe (11). A rotating shaft (141) is rotatably installed on the inner side of the guide frame (21). A rotating cylinder (22) is slidably fitted on the outer peripheral wall of the rotating shaft (141). A settling cavity (213) is opened on the inner side of the guide frame (21). The rotating cylinder (22) is movably installed on the inner side of the settling cavity (213). A guide cylinder (23) is slidably installed inside the inlet pipe (12). The rotating cylinder (22) is rotatably installed inside the guide cylinder (23). An impeller (143) is fixedly installed at the bottom of the rotating shaft (141). A guide wheel (142) is fixedly fitted on the side wall of the rotating shaft (141). The guide wheel (142) is located between the impeller (143) and the guide cylinder (23). A drive motor (14) is fixedly installed on the top of the guide frame (21). The drive motor (14) is located outside the drain pipe (1). The output shaft of the drive motor (14) is fixedly connected to the rotating shaft (141).

2. The noise-reducing high-temperature liquid metal circulating pump according to claim 1, characterized in that: The rotating cylinder (22) has a slide rod (221) integrally formed on its side wall. The inner side of the flow guide frame (21) is provided with a corrugated groove (216). The slide rod (221) is slidably installed inside the corrugated groove (216). A number of evenly distributed flow guide plates (212) are welded to the inner side of the flow guide frame (21).

3. The noise-reducing high-temperature liquid metal circulating pump according to claim 1, characterized in that: The rotating cylinder (22) has several evenly distributed spiral grooves (222) on its side wall, and several evenly distributed liquid inlet holes (223) are provided inside the rotating cylinder (22). The liquid inlet holes (223) and the spiral grooves (222) correspond to each other and are interconnected. The liquid inlet holes (223) are located inside the stationary cavity (213).

4. The noise-reducing high-temperature liquid metal circulating pump according to claim 3, characterized in that: The inner side of the guide tube (23) is welded with several evenly distributed guide vanes (231). The side walls of the guide vanes (231) are provided with air guide grooves (232). The top of the guide vanes (231) is provided with an air collection groove (233). The air guide grooves (232) and the air collection grooves (233) are connected. The air collection grooves (233) are located below the spiral grooves (222).

5. The noise-reducing high-temperature liquid metal circulating pump according to claim 3, characterized in that: The rotating cylinder (22) has an exhaust port three (225) inside. The exhaust port three (225) is connected to the inner side of the stationary cavity (213) and the guide frame (21) respectively. The stationary cavity (213) has a piston ring one (311) and a piston ring two (315) slidably installed inside. The piston ring one (311) is rotatably fitted on the outside of the rotating cylinder (22), and the piston ring two (315) is movably fitted on the outside of the rotating cylinder (22). The piston ring one (311) is located between the liquid inlet hole (223) and the exhaust port three (225), and the piston ring two (315) is located below the piston ring one (311).

6. The noise-reducing high-temperature liquid metal circulating pump according to claim 5, characterized in that: The bottom of the piston ring one (311) is integrally formed with a sealing plug (314), and the side wall of the piston ring two (315) is provided with a sealing hole (316). The sealing plug (314) is slidably inserted into the inside of the sealing hole (316), and the inside of the piston ring two (315) is hollow.

7. The noise-reducing high-temperature liquid metal circulating pump according to claim 5, characterized in that: The piston ring 1 (311) has an exhaust hole 4 (313) on its side wall. The top of the exhaust hole 4 (313) is provided with a one-way valve 1 (312). The side walls of the drain pipe (1) and the guide frame (21) are respectively provided with exhaust hole 1 (13) and exhaust hole 2 (211). The exhaust hole 1 (13) and exhaust hole 2 (211) correspond to each other.

8. The noise-reducing high-temperature liquid metal circulating pump according to claim 5, characterized in that: The bottom of the settling chamber (213) is provided with a drain hole (214). The end of the drain hole (214) connected to the guide pipe (11) is inclined upward. The drain hole (214) is located below the piston ring (315). The drain hole (214) is provided with a one-way pressure valve (215). The inlet hole (223) is provided with a one-way valve (224).

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