Automatic cleaning equipment for nuclear fuel pellets

Abstract

The invention provides automatic cleaning equipment for nuclear fuel pellets, belongs to the technical field of pellet cleaning, and solves the problems that in the prior art, the working efficiency is low, the labor intensity is large, and the time for operators to make contact with radioactive materials is long. The device comprises a protective cover, an ultrasonic cleaning device, a hot-air blower and a moving mechanism are installed on the inner side of the protective cover, a core block containing frame is connected to the moving mechanism, and the moving mechanism moves the core block containing frame to the ultrasonic cleaning device or the hot-air blower. The moving mechanism is arranged to move the pellet containing frame into the ultrasonic cleaning device to be cleaned or move the pellet containing frame to the hot-air blower to be dried, automatic cleaning and drying operation is achieved, the working intensity is reduced, a protective cover is arranged to isolate related equipment, and operators are prevented from making contact with radioactive materials for a long time. According to the cleaning equipment, small batches of pellets can be cleaned and dried at the same time, and the treatment efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of pellet cleaning, and in particular to automatic cleaning equipment for nuclear fuel pellets. Background Art

[0002] During the development and product sampling of nuclear fuel pellets, a large number of pellets need to be cleaned and dried according to their numbers to remove dirt and water stains on the surface of the pellets, providing clean and dry fuel pellet samples for subsequent analysis, characterization and qualification evaluation of the pellets.

[0003] The cleaning process of fuel pellets plays a vital role in the overall development, production and inspection process. For fuel pellets that need to be cleaned in different categories, the traditional cleaning method is to put the grinding qualified pellets into a small beaker or other sample container one by one, inject water or volatile cleaning liquid such as anhydrous ethanol into each sample container until it just covers the upper surface of the pellet, put it into an ultrasonic cleaner and clean it for 10 to 30 minutes according to the type of cleaning liquid, then pour out the cleaning waste liquid (radioactive waste liquid), and finally use a hair dryer or other tools to blow dry each pellet one by one for use. The above method has low work efficiency, high labor intensity, long operator contact time with radioactive materials, large amount of radioactive waste liquid generated and extremely high disposal cost, which is not suitable for the need to clean batch pellets during pellet development and product sampling. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide an automatic cleaning device for nuclear fuel pellets, in which a moving mechanism is provided to move the pellet placement frame to an ultrasonic cleaning device for cleaning or to a hot air blower for drying, thereby realizing automated cleaning and drying operations and reducing work intensity. A protective cover is provided to isolate related equipment to prevent operators from prolonged contact with radioactive materials. The cleaning device of the present application can clean and dry small batches of pellets at the same time, thereby improving processing efficiency.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A nuclear fuel pellet automatic cleaning device comprises a protective cover, an ultrasonic cleaning device, a hot air blower and a moving mechanism are installed on the inner side of the protective cover, a pellet placement frame is connected to the moving mechanism, and the moving mechanism moves the pellet placement frame to the ultrasonic cleaning device or the hot air blower; the moving mechanism comprises a horizontally arranged screw rod and a guide rod, the screw rod is rotatably connected to the protective cover, the screw rod is connected to a driving motor, a moving seat slidably connected to the guide rod is threadedly connected to the screw rod, and a telescopic device vertically arranged and used for driving the pellet placement frame to rise and fall is connected to the moving seat.

[0007] Preferably, the lower end of the telescopic device is connected to a connecting plate, a rotating motor is installed on the connecting plate, the rotating motor is connected to a vertically arranged output shaft and the output shaft is connected to the core block placement frame, a drying cylinder is installed on the hot air blower, an air outlet communicated with the hot air blower is arranged at the bottom of the drying cylinder, a water retaining cover is arranged on the inner wall of the drying cylinder, the water retaining cover is trumpet-shaped and the upper end opening diameter of the water retaining cover is smaller than the lower end opening diameter.

[0008] Preferably, the core block placement frame includes at least two mesh plates that are assembled and detachably connected to each other, a connecting seat is provided on the upper surface of the core block placement frame, a positioning rod is movably penetrated through the side wall of the connecting seat, a tension spring is sleeved on the positioning rod, one end of the tension spring is fixedly connected to the connecting seat, and the other end of the tension spring is fixedly connected to the positioning rod, a guide groove connected to the lower end face of the output shaft is vertically opened on the side wall of the output shaft, and a positioning groove cooperating with the positioning rod is opened in the guide groove.

[0009] Preferably, a plug is provided on the lower surface of the core block placement frame, a conical head is provided in the drying cylinder, a socket is provided at the upper end of the conical head, and a bearing movably matched with the plug is installed in the socket.

[0010] Preferably, the upper end of the water retaining cover is connected to a rubber water retaining ring, and a plurality of mutually fitting separation rubber plates are radially arranged on the rubber water retaining ring, and the separation rubber plates extend to directly below the conical head, and the diameter of the conical head is smaller than the diameter of the upper opening of the water retaining cover, and a lifting device connected to the conical head is vertically arranged at the bottom of the drying cylinder.

[0011] Preferably, a water baffle plate located above the core block placement frame is fixedly provided on the output shaft.

[0012] Preferably, the lower surface of the water baffle is provided with an annular groove, and the upper end surface of the drying cylinder is provided with a plurality of universal balls matched with the annular groove.

[0013] Preferably, a centrifugal filter device is provided on the outside of the protective cover, and a water inlet pipe and a water suction pipe are connected to the centrifugal filter device. The outlet of the water suction pipe extends into the ultrasonic cleaning device, and a suction pump is provided on the water suction pipe. The water inlet pipe is connected to a first drain pipe connected to the drying drum and a second drain pipe connected to the ultrasonic cleaning device, and valves are provided on the first drain pipe and the second drain pipe.

[0014] Preferably, the centrifugal filter device includes an outer shell with an opening at the upper end and a cover plate detachably connected to the outer shell, a stirring motor is arranged on the cover plate, the stirring motor is connected to a stirring shaft extending into the outer shell, the stirring shaft is provided with stirring blades, a filter screen is connected to the cover plate and covered on the outside of the stirring shaft, a water inlet pipe is located on the inner side of the filter screen, and a water suction pipe is located on the outer side of the filter screen.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0016] A moving mechanism is provided to move the core block placement frame to an ultrasonic cleaning device for cleaning or to a hot air blower for drying, thereby realizing automated cleaning and drying operations and reducing work intensity. A protective cover is provided to isolate related equipment to prevent operators from prolonged contact with radioactive materials. The cleaning equipment of the present application can clean and dry small batches of core blocks at the same time, thereby improving processing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A schematic diagram of a front cross-sectional structure provided by an embodiment of the present invention;

[0019] Figure 2 A schematic diagram of the structure of a drying drum provided by an embodiment of the present invention;

[0020] Figure 3 A schematic diagram of the core block placement frame structure provided by an embodiment of the present invention;

[0021] Figure 4 A schematic structural diagram of a centrifugal filter device provided in an embodiment of the present invention;

[0022] Figure 5 A schematic diagram of the structure of a rubber water retaining ring provided in an embodiment of the present invention;

[0023] Figure 6 A schematic diagram of a drying state provided by an embodiment of the present invention;

[0024] Figure 7 A schematic diagram of a drying state provided by an embodiment of the present invention.

[0025] Figure numerals: 1-ultrasonic cleaning device; 2-hot air blower; 3-first drain pipe; 4-second drain pipe; 5-water inlet pipe; 6-centrifugal filter device; 601-housing; 602-stirring motor; 603-cover plate; 604-stirring blade; 605-filter screen; 606-stirring shaft; 7-water suction pipe; 8-suction pump; 9-annular groove; 10-sealing door; 11-protective cover; 12-moving seat; 13-position sensor; 14-screw rod; 15-guide rod; 16-drive motor; 17-suction pipe; 18- Universal ball; 19-drying cylinder; 20-water retaining cover; 21-air outlet; 22-telescopic device; 23-rotating motor; 24-connecting plate; 25-water retaining plate; 26-core block placement frame; 2601-mesh plate; 2602-plug; 2603-connecting seat; 2604-tension spring; 2605-positioning rod; 27-core block; 28-bearing; 29-socket; 30-conical head; 31-rubber water retaining ring; 32-lifting device; 33-output shaft; 34-guide groove; 35-positioning groove; 36-separation rubber plate. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the description of the present invention, it should be noted that if the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the product of the application is usually placed when used. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0029] Combine the following Figure 1-Figure 7 The present invention is described in detail.

[0030] Example

[0031] An automatic cleaning device for nuclear fuel pellets comprises a protective cover 11, an ultrasonic cleaning device 1, a hot air blower 2 and a moving mechanism are installed inside the protective cover 11, a pellet placement frame 26 is connected to the moving mechanism, and the moving mechanism moves the pellet placement frame 26 to the ultrasonic cleaning device 1 or the hot air blower 2.

[0032] The moving mechanism has at least the function of moving the core block placement frame 26 horizontally and the function of lifting and lowering the core block placement frame 26, ensuring that the moving mechanism can move the core block placement frame 26 containing the core blocks 27 to the ultrasonic cleaning device 1 for cleaning and move the core blocks 27 to the hot air blower 2 for drying.

[0033] The core block placement frame 26 is detachably connected to the moving mechanism to facilitate the replacement of the core block 27; a sealing door 10 is provided on the protective cover 11 for taking and placing the core block placement frame 26; the protective cover 11 can be set to be transparent to facilitate checking whether the internal cleaning process is proceeding smoothly; the ultrasonic cleaning device 1 can be provided with a heating device to heat the cleaning liquid to increase the cleaning effect.

[0034] The moving mechanism includes a screw rod 14 and a guide rod 15 arranged horizontally. The screw rod 14 is rotatably connected to the protective cover 11. The screw rod 14 is connected to a driving motor 16. The screw rod 14 is threadedly connected to a moving seat 12 slidably connected to the guide rod 15. The moving seat 12 is connected to a telescopic device 22 arranged vertically and used to drive the core block placement frame 26 to rise and fall. The screw rod 14 rotates to make the moving seat 12 move laterally, thereby realizing the lateral movement of the core block placement frame 26. The telescopic device 22 lifts and lowers the core block placement frame 26. Among them, at least two position sensors 13 for monitoring the position of the moving seat 12 are arranged on the protective cover 11, so that the moving seat 12 can be accurately moved to the top of the ultrasonic cleaning device 1 and the top of the hot air blower 2; the protective cover 11 is provided with a suction pipe 17 to suck the moisture and gas generated during the drying process into other processing equipment to ensure that the radioactive aerosol and dust in the cleaning process of the core block 27 do not enter the open environment.

[0035] The lower end of the telescopic device 22 is connected to a connecting plate 24, and a rotating motor 23 is installed on the connecting plate 24. The rotating motor 23 is connected to a vertically arranged output shaft 33, and the output shaft 33 is connected to the core block placement frame 26. A drying cylinder 19 is installed on the hot air blower 2, and an air outlet 21 communicated with the hot air blower 2 is arranged at the bottom of the drying cylinder 19. A water retaining cover 20 is arranged on the inner wall of the drying cylinder 19. The water retaining cover 20 is trumpet-shaped and the upper end opening diameter of the water retaining cover 20 is smaller than the lower end opening diameter.

[0036] The trumpet-shaped water shield 20 cooperates with the drying drum 19 to form a water collecting tank structure, so as to facilitate the collection of the thrown-out cleaning liquid. The rotating motor 23 can rotate the pellet placement frame 26, and after cooperating with the drying drum 19, most of the cleaning liquid attached to the pellet 27 can be thrown out of the pellet placement frame 26, and the thrown-out cleaning liquid is collected on the water shield 20, so as to increase the drying efficiency of the hot air blower 2 for the pellet 27.

[0037] The core block placement frame 26 includes at least two mesh plates 2601 that are assembled and detachably connected to each other. A connecting seat 2603 is provided on the upper surface of the core block placement frame 26. A positioning rod 2605 is movably penetrated through the side wall of the connecting seat 2603. A tension spring 2604 is sleeved on the positioning rod 2605. One end of the tension spring 2604 is fixedly connected to the connecting seat 2603, and the other end of the tension spring 2604 is fixedly connected to the positioning rod 2605. A guide groove 34 connected to the lower end face of the output shaft 33 is vertically opened on the side wall of the output shaft 33, and a positioning groove 35 cooperating with the positioning rod 2605 is opened in the guide groove 34. The two mesh plates 2601 can be connected by screws. After the two mesh plates 2601 are assembled, the core block 27 is enclosed in a mesh space, so that the core block 27 can be easily cleaned and dried. In order to facilitate the quick placement of the core block placement frame 26, a positioning rod 2605 is provided to cooperate with the positioning groove 35 to install the core block placement frame 26 on the output shaft 33. In the process of inserting the output shaft 33 into the connecting seat 2603, the positioning rod 2605 also cooperates with the guide groove 34, so that the output shaft 33 can only slide axially relative to the connecting seat 2603, so that the positioning rod 2605 can be quickly inserted into the positioning groove 35. When the positioning rod 2605 is aligned with the positioning groove 35, the tension spring 2604 pulls the positioning rod 2605 into the positioning groove 35 to achieve locking. When removing the core block placement frame 26, it is only necessary to pull the positioning rod 2605 out of the positioning groove 35, and the core block placement frame 26 is separated from the output shaft 33 due to gravity.

[0038] The lower surface of the pellet placement frame 26 is provided with a plug 2602, and the drying drum 19 is provided with a conical head 30, and the upper end of the conical head 30 is provided with a socket 29, and the socket 29 is installed with a bearing 28 that flexibly cooperates with the plug 2602. The lower end of the plug 2602 is arc-shaped, which is convenient for inserting into the bearing 28; when the moving mechanism moves the pellet placement frame 26 to the top of the drying drum 19 and extends into the drying drum 19, the plug 2602 is inserted into the bearing 28, and during the process of the pellet placement frame 26 rotating and drying, the stability of the pellet placement frame 26 can be maintained, and the moving mechanism is prevented from being damaged due to the unstable swing of the pellet placement frame 26.

[0039] The upper end of the water retaining cover 20 is connected to a rubber water retaining ring 31, and a plurality of mutually fitting separation rubber plates 36 are radially arranged on the rubber water retaining ring 31. The separation rubber plates 36 extend to directly below the conical head 30. The diameter of the conical head 30 is smaller than the diameter of the upper opening of the water retaining cover 20. A lifting device 32 connected to the conical head 30 is vertically arranged at the bottom of the drying cylinder 19. The lifting device 32 can drive the conical head 30 to move up and down, so as to adjust the position. When the conical head 30 is located above the rubber water retaining ring 31, the core block placement frame 26 needs to be spun dry. The conical head 30 cooperates with the separation rubber plate 36 to guide the cleaning liquid dripping from the core block placement frame 26 to the water retaining cover 20 before spun dry, so as to prevent the cleaning liquid from entering the hot air blower 2 and causing damage. After the spun dry is completed, the conical head 30 moves to the bottom of the rubber water retaining ring 31, and the hot air blower 2 works to generate hot air. The hot air passes through the inclined surface of the conical head 30 and the water retaining cover 20 and converges to the middle part, thereby reducing the loss of wind force. The multiple separation rubber plates 36 are provided, and the separation rubber plates 36 can be bent and deformed during the conical head 30 passing through, so as to facilitate the conical head 30 to pass through.

[0040] A water baffle 25 located above the core block placement frame 26 is fixedly arranged on the output shaft 33. The water baffle 25 can prevent the cleaning liquid from hitting the drying drum 19 and splashing out of the drying drum 19 to cause pollution during the spin-drying process.

[0041] The lower surface of the water baffle 25 is provided with an annular groove 9, and the upper end surface of the drying cylinder 19 is provided with a plurality of universal balls 18 that cooperate with the annular groove 9. The water baffle 25 cooperates with the universal balls 18 to further increase the rotational stability of the core block placement frame 26. During the spin-drying process, the water baffle 25 needs to maintain contact with the universal balls 18. During the drying process, the telescopic device 22 needs to be raised a certain distance to leave a gap for gas flow between the water baffle 25 and the upper end surface of the drying cylinder 19; during the drying process, the core block placement frame 26 can be slowly rotated to generate turbulence in the hot air of the drying, thereby evenly drying the core blocks 27.

[0042] A centrifugal filter device 6 is arranged outside the protective cover 11, and a water inlet pipe 5 and a water extraction pipe 7 are connected to the centrifugal filter device 6, and the outlet of the water extraction pipe 7 extends into the ultrasonic cleaning device 1, and a suction pump 8 is arranged on the water extraction pipe 7. The water inlet pipe 5 is connected to a first drain pipe 3 connected to the drying drum 19 and a second drain pipe 4 connected to the ultrasonic cleaning device 1, and valves are arranged on the first drain pipe 3 and the second drain pipe 4. The pipe mouth of the first drain pipe 3 is located at the intersection of the inclined outer wall of the water shield 20 and the inner wall of the drying drum 19. The cleaning liquid in the ultrasonic cleaning device 1 and the drying drum 19 can enter the centrifugal filter device 6 through the pipeline to filter impurities, so that the cleaning liquid can be reused in the ultrasonic cleaning device 1, avoiding the generation of excessive radioactive waste liquid, and reducing the treatment cost of radioactive waste liquid.

[0043] The centrifugal filter device 6 includes a shell 601 with an opening at the upper end and a cover plate 603 detachably connected to the shell 601, a stirring motor 602 is arranged on the cover plate 603, the stirring motor 602 is connected to a stirring shaft 606 extending into the shell 601, the stirring shaft 606 is provided with stirring blades 604, a filter screen 605 covered on the outside of the stirring shaft 606 is connected to the cover plate 603, the water inlet pipe 5 is located on the inner side of the filter screen 605, and the water suction pipe 7 is located on the outer side of the filter screen 605.

[0044] The stirring motor 602 drives the stirring shaft 606 and the stirring blade 604 to rotate, stirring the cleaning liquid at high speed, and the cleaning liquid generates centrifugal force to accelerate through the filter 605, thereby improving the filtering efficiency. After using for a period of time, the cover plate 603 can be opened to clean the filter 605; the connection between the filter 605 and the cover plate 603, and the connection between the cover plate 603 and the housing 601 can be connected by screws, which is convenient for disassembly.

[0045] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An automatic cleaning device for nuclear fuel pellets, characterized in that: The invention comprises a protective cover (11), wherein an ultrasonic cleaning device (1), a hot air blower (2) and a moving mechanism are installed on the inner side of the protective cover (11), a core block placement frame (26) is connected to the moving mechanism, and the moving mechanism moves the core block placement frame (26) to the ultrasonic cleaning device (1) or the hot air blower (2); the moving mechanism comprises a horizontally arranged screw rod (14) and a guide rod (15), wherein the screw rod (14) is rotatably connected to the protective cover (11), the screw rod (14) is connected to a driving motor (16), a moving seat (12) slidably connected to the guide rod (15) is threadedly connected to the screw rod (14), and a telescopic device (22) is connected to the moving seat (12) which is vertically arranged and used for driving the core block placement frame (26) to rise and fall.

2. The automatic cleaning device for nuclear fuel pellets according to claim 1, characterized in that: The lower end of the telescopic device (22) is connected to a connecting plate (24), a rotating motor (23) is installed on the connecting plate (24), the rotating motor (23) is connected to a vertically arranged output shaft (33), and the output shaft (33) is connected to a core block placement frame (26), a drying cylinder (19) is installed on the hot air blower (2), an air outlet (21) communicating with the hot air blower (2) is arranged at the bottom of the drying cylinder (19), and a water shield (20) is arranged on the inner wall of the drying cylinder (19), the water shield (20) is trumpet-shaped, and the upper end opening diameter of the water shield (20) is smaller than the lower end opening diameter.

3. The automatic cleaning device for nuclear fuel pellets according to claim 2, characterized in that: The core block placement frame (26) comprises at least two mesh plates (2601) which are assembled and detachably connected to each other. A connecting seat (2603) is arranged on the upper surface of the core block placement frame (26). A positioning rod (2605) is movably penetrated through the side wall of the connecting seat (2603). A tension spring (2604) is sleeved on the positioning rod (2605). One end of the tension spring (2604) is fixedly connected to the connecting seat (2603), and the other end of the tension spring (2604) is fixedly connected to the positioning rod (2605). A guide groove (34) which is in communication with the lower end surface of the output shaft (33) is vertically provided on the side wall of the output shaft (33). A positioning groove (35) which cooperates with the positioning rod (2605) is provided in the guide groove (34).

4. The automatic cleaning device for nuclear fuel pellets according to claim 2, characterized in that: A plug (2602) is provided on the lower surface of the core block placement frame (26), a conical head (30) is provided in the drying cylinder (19), a socket (29) is provided at the upper end of the conical head (30), and a bearing (28) movably matched with the plug (2602) is installed in the socket (29).

5. The automatic cleaning device for nuclear fuel pellets according to claim 4, characterized in that: The upper end of the water retaining cover (20) is connected to a rubber water retaining ring (31), and a plurality of mutually fitting separation rubber plates (36) are radially arranged on the rubber water retaining ring (31). The separation rubber plates (36) extend to the bottom of the conical head (30). The diameter of the conical head (30) is smaller than the diameter of the upper opening of the water retaining cover (20). A lifting device (32) connected to the conical head (30) is vertically arranged at the bottom of the drying cylinder (19).

6. The automatic cleaning device for nuclear fuel pellets according to claim 2, characterized in that: A water baffle (25) located above the core block placement frame (26) is fixedly arranged on the output shaft (33).

7. The automatic cleaning device for nuclear fuel pellets according to claim 6, characterized in that: The lower surface of the water baffle plate (25) is provided with an annular groove (9), and the upper end surface of the drying cylinder (19) is provided with a plurality of universal balls (18) matched with the annular groove (9).

8. The automatic cleaning device for nuclear fuel pellets according to claim 2, characterized in that: A centrifugal filter device (6) is arranged outside the protective cover (11), a water inlet pipe (5) and a water extraction pipe (7) are connected to the centrifugal filter device (6), an outlet of the water extraction pipe (7) extends into the ultrasonic cleaning device (1), a suction pump (8) is arranged on the water extraction pipe (7), a first drain pipe (3) connected to the drying drum (19) and a second drain pipe (4) connected to the ultrasonic cleaning device (1) are connected to the water inlet pipe (5), and valves are arranged on the first drain pipe (3) and the second drain pipe (4).

9. The automatic cleaning device for nuclear fuel pellets according to claim 8, characterized in that: The centrifugal filtering device (6) comprises a housing (601) with an opening at the upper end and a cover plate (603) detachably connected to the housing (601); a stirring motor (602) is arranged on the cover plate (603); the stirring motor (602) is connected to a stirring shaft (606) extending into the housing (601); a stirring blade (604) is arranged on the stirring shaft (606); a filter screen (605) is connected to the cover plate (603) and is covered on the outside of the stirring shaft (606); a water inlet pipe (5) is located on the inner side of the filter screen (605); and a water extraction pipe (7) is located on the outer side of the filter screen (605).

Images