Integrated filter device with refrigeration function

Abstract

The utility model belongs to the technical field of semiconductor processing, disclose a kind of integrated filter device with refrigeration function, it includes shell, filter assembly for filtering grinding fluid is provided in shell, cooling assembly for heat exchange with grinding fluid, and with filter assembly communication to store the clean liquid tank of filtered grinding fluid;The cooling pipe of cooling assembly is located in clean liquid tank, for cooling grinding fluid by coolant, shell is also equipped with the cooling fan for cooling assembly heat dissipation.Therefore the filter device when using, cold zone component and filter assembly are integrated in shell, and cooling pipe is built-in in clean liquid tank, so that coolant and grinding fluid between heat exchange efficiency is higher, ensure that the temperature of grinding fluid in clean liquid tank can be accurately maintained in certain range, simultaneously still can make overall volume smaller, space is less, to improve the adaptability of the device overall to environment.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductor processing, in particular to an integrated filtering device with a refrigeration function. Background Art

[0002] In the semiconductor processing industry, grinding processing is widely used. The used grinding fluid needs to be precisely filtered before it can be recycled. For occasions equipped with small integrated filtering devices, although their precision filtering units can effectively ensure the filtering accuracy, as the grinding fluid is continuously used, the heat generated during the processing will cause the temperature of the grinding fluid to continuously rise. This not only affects the stability and precision of the processing process, but also makes it lose its crucial cooling function.

[0003] Therefore, such small integrated filtering systems must be equipped with a supporting external air-cooled chiller to cool the grinding fluid. Different from the water-cooled chiller that requires the client to provide external cooling water and has relatively high construction and operation costs, the air-cooled chiller can meet the refrigeration requirements with its own design, does not rely on external cooling facilities, has stronger adaptability, and is particularly suitable for application scenarios with limited space and facilities.

[0004] Currently, the common refrigeration principle of the air-cooled chiller supporting small integrated filtering devices is as follows: The grinding fluid in the liquid storage tank of the integrated filtering device is pumped out by a circulation pump and sent into the evaporator inside the external chiller. Inside the evaporator, the pipeline where the grinding fluid flows and the pipeline where the low-temperature refrigerant (refrigerant) flowing independently inside the chiller conduct indirect heat exchange (usually through heat exchange on the pipe wall), and the heat of the grinding fluid is absorbed by the refrigerant and thus cooled. The cooled grinding fluid flows back to the water tank of the integrated filtering device. This process depends on the circulation pump and the connecting pipeline system. It should be noted that this refrigeration system includes an independent refrigerant circulation loop, which will occupy additional space as part of the overall solution. Moreover, this indirect heat exchange method through the evaporator has the problem of low heat exchange efficiency, resulting in high energy consumption during the operation of the system. Content of the Utility Model

[0005] The purpose of the utility model is to provide an integrated filtering device with a refrigeration function, and solve the problems of low heat exchange efficiency and poor temperature control accuracy when the grinding fluid is filtered and refrigerated in the prior art.

[0006] To achieve this purpose, the utility model adopts the following technical solutions:

[0007] In a first aspect, this application provides an integrated filtration device with a cooling function, comprising a housing, wherein a filtration assembly for filtering grinding fluid, a cooling assembly for heat exchange with the grinding fluid, and a clean liquid tank connected to the filtration assembly for storing the filtered grinding fluid are disposed within the housing; the cooling pipe of the cooling assembly is located in the clean liquid tank and is used to cool the grinding fluid with a refrigerant; the housing is also provided with a cooling fan for dissipating heat from the cooling assembly.

[0008] Optionally, the cooling assembly includes a compressor, a condenser, a filter, an expansion valve, and a refrigerant storage tank. The above components and the cooling pipes arranged in the clean liquid tank are connected in sequence through connecting pipes to form a one-way closed-loop refrigeration circuit.

[0009] Wherein: the inlet end of the cooling pipe is connected to the expansion valve, the outlet end is connected to the inlet of the refrigerant storage tank, and the outlet of the refrigerant storage tank is connected to the suction end of the compressor.

[0010] Optionally, a portion of the cooling pipe extends bent within the clean liquid tank.

[0011] Optionally, the condenser of the condensing unit is located at the top inside the housing.

[0012] Optionally, the compressor and the refrigerant storage tank are placed above the clean liquid tank, the condenser is placed above the filter assembly, and the filter and the expansion valve are placed on the pipeline connecting the condenser and the cooling pipe.

[0013] Optionally, the cooling fan is disposed on the top wall of the housing and vertically covers the heat dissipation surface of the condenser.

[0014] Optionally, the filtering component includes:

[0015] Filter pumps are used to extract grinding fluid;

[0016] The filter tank is connected to both the filter pump and the clean liquid tank. The filter tank is used to filter the grinding fluid pumped by the filter pump and then guide it into the clean liquid tank.

[0017] Optionally, the filter tank is provided with a filter inlet connected to the filter pump and a filter outlet connected to the purified liquid tank.

[0018] Optionally, the integrated filtration device with cooling function further includes:

[0019] A temperature detector is installed inside the clean liquid tank and is connected to the cooling assembly via an electronic control unit. The temperature detector is used to detect the temperature inside the clean liquid tank.

[0020] Optionally, the integrated filtration device with cooling function further includes:

[0021] A liquid supply pump, connected to the clean liquid tank, injects the cooled grinding fluid from the clean liquid tank into the machine tool; and / or,

[0022] A dirty fluid tank has a dirty fluid inlet, which is connected to the grinding fluid outlet of the machine tool, and a filter pump is connected to the dirty fluid tank to extract the grinding fluid from the dirty fluid tank.

[0023] The beneficial effects of this utility model are:

[0024] The grinding fluid is extracted and filtered through a filtration assembly to meet circulation requirements before being channeled into a clean fluid tank for storage. When the temperature of the grinding fluid in the clean fluid tank is high, the cooling assembly activates, introducing cooler refrigerant through cooling pipes into the clean fluid tank. Heat exchange between the refrigerant and the grinding fluid in the tank lowers the temperature. A cooling fan dissipates heat from the cooling assembly, ensuring its continuous operation. Therefore, in use, the high-temperature grinding fluid containing impurities flowing from the machine tool is first filtered and stored in the clean fluid tank. At this point, the grinding fluid delivery does not require complex piping; simply connecting the filtration assembly to the clean fluid tank is sufficient. The cooling pipes are directly installed inside the clean fluid tank, allowing direct contact with the grinding fluid for efficient heat exchange, improving cooling efficiency and ensuring the grinding fluid temperature in the clean fluid tank is precisely maintained within a certain range. Furthermore, the built-in design of the cooling assembly contributes to the overall compact size and space-saving design of the device, enhancing its environmental adaptability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the internal structure of an integrated filter device with cooling function according to an embodiment of this utility model;

[0026] Figure 2 This is a schematic diagram of the structure of an integrated filter device with cooling function after the housing is installed in an embodiment of this utility model;

[0027] Figure 3 This is a first side view of an integrated filtration device with cooling function in this embodiment of the present invention, after concealing the dirty liquid tank and the clean liquid tank.

[0028] Figure 4 This is a second side view of an integrated filtration device with cooling function in this embodiment of the present invention, after concealing the dirty liquid tank and the clean liquid tank.

[0029] In the picture:

[0030] 1. Dirty liquid tank; 2. Filter assembly; 21. Filter pump; 22. Filter canister; 3. Clean liquid tank; 4. Cooling assembly; 41. Refrigerant storage tank; 42. Compressor; 43. Cooling pipe; 44. Condenser; 45. Filter; 46. Expansion valve; 5. Cooling fan; 6. Housing; 60. Heat dissipation vent; 61. Electrical control unit; 7. Temperature detector; 8. Liquid supply pump; 9. Casters. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, not the entire structure.

[0032] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0033] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, 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 utility model. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning.

[0035] This application provides an integrated filtration device with a cooling function (hereinafter referred to as "the filtration device").

[0036] Reference Figures 1 to 4 The filtration device includes a housing 6. Inside the housing 6 are a filter assembly 2 for filtering the grinding fluid, a cooling assembly 4 for heat exchange with the grinding fluid, and a clean fluid tank 3 connected to the filter assembly 2 to store the filtered grinding fluid. The cooling pipe 43 of the cooling assembly 4 is located in the clean fluid tank 3 and is used to cool the grinding fluid with a refrigerant. The housing 6 also has a cooling fan 5 for dissipating heat from the cooling assembly 4.

[0037] The device also includes a dirty fluid tank 1. The dirty fluid tank 1 has a dirty fluid inlet for connecting to the grinding fluid outlet of the machine tool, and a filter assembly 2 is connected to the dirty fluid tank 1 to extract the grinding fluid in the dirty fluid tank 1.

[0038] Specifically, the dirty liquid tank 1 is connected to the machine tool via a return pipe to recover used grinding fluid and other liquids. The clean liquid tank 3 can be independent of the dirty liquid tank 1, or the two can be integrated into one unit, i.e., the tank is divided into two parts by a partition or other structure, with one side serving as the dirty liquid tank 1 and the other as the clean liquid tank 3. The specific design can be determined based on the actual installation space. Casters 9 can be installed on the bottom walls of both the dirty liquid tank 1 and the clean liquid tank 3 to facilitate overall movement.

[0039] In this embodiment, a housing 6 is provided on the upper side of the dirty liquid tank 1 and the clean liquid tank 3. The housing 6 can cover both the filter assembly 2 and the cooling assembly 4, so that the entire device is integrated inside the housing 6. In other embodiments, the dirty liquid tank 1 and the clean liquid tank 3 may both be located inside the housing 6, or one of the dirty liquid tank 1 and the clean liquid tank 3 may be located inside the housing 6. The specific design can be based on the actual usage environment. The filter assembly 2 can be set on the top wall of the dirty liquid tank 1, overlapping with the dirty liquid tank 1. The filter assembly 2 can continuously extract the grinding fluid from the dirty liquid tank 1 and inject the filtered grinding fluid into the clean liquid tank 3. The specific filtration structure can be designed according to the filtration requirements of the grinding fluid. It can refer to the prior art, and this application does not impose too many limitations on it.

[0040] The cooling assembly 4 has a condensation structure and a heat exchange structure. The heat exchange structure is a cooling pipe 43, which is made of a material with good thermal conductivity, such as metal. The cooling pipe 43 is located inside the clean liquid tank 3, where refrigerant can continuously flow. The grinding fluid in the clean liquid tank 3 can form efficient heat exchange with the refrigerant through the pipe wall of the cooling pipe 43, thereby achieving temperature control. The cooling fan 5 is positioned directly opposite the condensation structure to dissipate heat from it, ensuring that the cooling assembly 4 can operate continuously for extended periods.

[0041] By setting up a dirty liquid tank 1 and a clean liquid tank 3, the grinding fluid flows out of the machine and enters the dirty liquid tank 1. The filter assembly 2 extracts and filters the grinding fluid to meet the circulation requirements and then guides it to the clean liquid tank 3 for storage. When the temperature of the grinding fluid in the clean liquid tank 3 is high, the cooling assembly 4 is activated to introduce the cooler refrigerant into the clean liquid tank 3 through the cooling pipe 43. After the refrigerant exchanges heat with the grinding fluid in the clean liquid tank 3, the temperature of the grinding fluid can be reduced. The cooling fan 5 can dissipate heat from the cooling assembly 4, so that the cooling assembly 4 can operate continuously. Therefore, when this filtration device is in use, the high-temperature grinding fluid containing impurities flowing from the machine tool can be filtered and stored in the clean fluid tank 3. At this time, the delivery of the grinding fluid does not require a complex pipeline layout; it is only necessary to connect the filter assembly 2 to the clean fluid tank 3. The cooling pipe 43 is directly installed in the clean fluid tank 3, allowing the cooling pipe 43 to directly contact the grinding fluid. The two can fully achieve heat exchange, improve the cooling effect of the grinding fluid, improve heat exchange efficiency, and ensure that the temperature of the grinding fluid in the clean fluid tank 3 can be accurately maintained within a certain range. Furthermore, the partially built-in design of the cooling assembly 4 also makes the overall device smaller in size and occupies less space, thereby improving the overall adaptability of the device to the environment.

[0042] Optionally, the cooling assembly 4 includes a refrigerant tank 41, a compressor 42, a condenser 44, a filter 45, and an expansion valve 46. These components are sequentially connected to the cooling pipe 43 arranged in the clean liquid tank 3 via connecting pipes to form a unidirectional closed-loop refrigeration circuit. Specifically, the inlet end of the cooling pipe 43 is connected to the expansion valve 46, the outlet end is connected to the inlet of the refrigerant tank 41, and the outlet of the refrigerant tank 41 is connected to the suction end of the compressor 42.

[0043] Specifically, the refrigerant storage tank 41 is used to store refrigerant; the compressor 42 is connected to the refrigerant storage tank 41 to extract refrigerant; the condensing unit is connected to the compressor 42 to cool the refrigerant extracted by the compressor 42; one end of the cooling pipe 43 is connected to the condensing unit, and the other end passes through the clean liquid tank 3 and is connected to the refrigerant storage tank 41. The refrigerant cooled by the condensing unit flows back to the refrigerant storage tank 41 through the cooling pipe 43.

[0044] The refrigerant storage tank 41, compressor 42, and other structures can be installed above the clean liquid tank 3. The compressor 42 compresses the refrigerant and sends it to the condenser 44 for condensation. After condensation, the refrigerant is sent into the cooling pipe 43, which passes through the clean liquid tank 3 and connects to the refrigerant storage tank 41. This allows the refrigerant to flow into the clean liquid tank 3 to exchange heat with the grinding fluid. After the heat exchange is complete, the refrigerant flows back to the refrigerant storage tank 41 for storage, enabling the refrigerant to be recycled. The cooling pipe 43 is located inside the clean liquid tank 3, so that the refrigerant and grinding fluid are separated only by the wall thickness of the cooling pipe 43. The cooling pipe 43 is made of a material with good thermal conductivity, which allows for better heat exchange efficiency between the refrigerant and the grinding fluid, thereby improving the cooling effect on the grinding fluid.

[0045] Optionally, the portion of the cooling pipe 43 within the clean liquid tank 3 is bent and extended.

[0046] Specifically, the cooling pipe 43 can be a coil, or it can be any combination of spiral bends, S-shaped bends, or disordered stacking. The specific bend shape is not limited in this application. Furthermore, the cooling pipe 43 can be arranged vertically or horizontally, and the specific arrangement can be designed according to the dimensions of the clean liquid tank 3. By bending and extending the cooling pipe 43, its length can be effectively increased within a limited space, allowing the refrigerant to remain in the clean liquid tank 3 for a sufficient time, thereby further improving the heat exchange effect and thus enhancing the cooling effect.

[0047] Optionally, the condenser 44 of the condensing unit is located at the top inside the housing 6.

[0048] Specifically, the condenser 44 is positioned near the inner top of the housing 6, allowing the heat generated during operation to be quickly transferred to the outside. This facilitates heat dissipation from the condenser 44 and reduces the likelihood of heat transfer into the water tank. Multiple ventilation openings 60 can also be provided on the housing 6 to improve airflow and further enhance heat dissipation. These openings 60 are triangular in shape, serving not only for airflow but also as through-holes for personnel to pass through the interior.

[0049] Optionally, the compressor 42 and refrigerant tank 41 are placed above the clean liquid tank 3, the condenser 44 is placed above the filter assembly 2, and the filter 45 and expansion valve 46 are placed on the pipeline connecting the condenser 44 and the cooling pipe 43. Specifically, a suitable space is selected above the clean liquid tank 3 and the filter assembly 2 to install the compressor 42, refrigerant tank 41, condenser 44, and other structures, so that the structure of the entire device is distributed from top to bottom and can all be covered by the housing 6, thereby further improving the compactness between the various structures and reducing the space occupied.

[0050] Optionally, the cooling fan 5 is mounted on the top wall of the housing 6 and vertically covers the heat dissipation surface of the condenser 44.

[0051] Specifically, the cooling fan 5 is integrated in the middle of the top wall of the housing 6, and its air outlet is vertically covered by the condenser 44 to cool the condenser 44, ensuring that the condenser 44 can operate continuously, thereby continuously controlling the temperature of the grinding fluid in the clean fluid tank 3.

[0052] Optionally, the filter assembly 2 includes a filter pump 21 and a filter tank 22. The filter pump 21 is used to draw grinding fluid from the dirty fluid tank 1; the filter tank 22 is connected to the filter pump 21 and the clean fluid tank 3 respectively, and the filter tank 22 is used to filter the grinding fluid drawn out by the filter pump 21 and guide it into the clean fluid tank 3.

[0053] Specifically, the filter pump 21 is installed on the dirty liquid tank 1, and its outlet is connected to the inlet of the filter tank 22. Its inlet is connected to the dirty liquid tank 1 through a pipeline to draw the grinding fluid in the dirty liquid tank 1 into the filter tank 22. A filtration structure is installed in the filter tank 22. The grinding fluid can be precisely filtered as it flows from the inlet to the outlet of the filter tank 22. After filtration, the grinding fluid is discharged through the outlet of the filter tank 22 and enters the clean liquid tank 3.

[0054] Optionally, the filter tank 22 is provided with a filter inlet connected to the filter pump 21 and a filter outlet connected to the clean liquid tank 3.

[0055] Specifically, the filter tank 22 is cylindrical and extends vertically. A filter element is installed inside the filter tank 22 to achieve precision filtration of the grinding fluid. The specific structure of the filter element can be found in existing technology and will not be elaborated here. In this embodiment, a filter inlet is provided at the lower end of the filter tank 22, and the lower end is embedded in the dirty fluid tank 1 to reduce its upper height, thereby reducing the maximum height of the filter tank 22 and further reducing the overall size and volume of the device, thus reducing space occupation. A filter outlet is provided at the upper end of the filter tank 22 so that the grinding fluid enters from the lower end of the filter tank 22, completes precision filtration through the filter element, and then flows out from the upper outlet of the filter tank 22. In other embodiments, the filter inlet and filter outlet can also be specifically set according to the actual flow direction of the grinding fluid, and are not limited to the upper and lower ends mentioned above.

[0056] Optionally, the filtration device also includes a liquid supply pump 8. The liquid supply pump 8 is connected to the clean liquid tank 3 to inject the cooled grinding fluid in the clean liquid tank 3 into the machine tool.

[0057] Specifically, the fluid supply pump 8 is located above the clean fluid tank 3, with its suction port connected to the clean fluid tank 3 and its outlet connected to the machine tool via a pipeline. During machine tool operation, the fluid supply pump 8 continuously draws grinding fluid from the clean fluid tank 3 and injects it into the machine tool, thus enabling the grinding fluid to be recycled. Simultaneously, the fluid supply pump 8 is also integrated inside the inner casing to further reduce the space occupied by the external components.

[0058] Optionally, the filtration device also includes a temperature detector 7. The temperature detector 7 is located inside the clean liquid tank 3 and is connected to the cooling assembly 4 via an electronic control unit 61. The temperature detector 7 is used to detect the temperature inside the clean liquid tank 3.

[0059] Specifically, an electronic control unit 61 is installed on the side of the housing 6. A temperature detector 7 is connected to the cooling assembly 4 via the electronic control unit 61. The temperature detector 7 can detect the temperature of the grinding fluid in the clean fluid tank 3 and feed it back to the electronic control unit 61. The electronic control unit 61 can compare the temperature with a threshold. When the temperature is higher than the threshold, it indicates that the temperature of the grinding fluid in the clean fluid tank 3 is too high and cooling is required. At this time, the electronic control unit 61 can generate a start signal to control the cooling assembly 4 to start. By setting up the electronic control unit 61, the entire equipment can be automated, further improving the accuracy of temperature control.

[0060] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. Those skilled in the art can make various obvious changes, readjustments, and substitutions without departing from the protection scope of this utility model. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. An integrated filter device with a cooling function, comprising a housing (6), characterized in that, The housing (6) is provided with a filter assembly (2) for filtering the grinding fluid, a cooling assembly (4) for exchanging heat with the grinding fluid, and a clean liquid tank (3) connected to the filter assembly (2) to store the filtered grinding fluid; the cooling pipe (43) of the cooling assembly (4) is located in the clean liquid tank (3) and is used to cool the grinding fluid with a refrigerant; the housing (6) is also provided with a cooling fan (5) for dissipating heat from the cooling assembly (4).

2. The integrated filter device with cooling function according to claim 1, characterized in that, The cooling assembly (4) includes a compressor (42), a condenser (44), a filter (45), an expansion valve (46), and a refrigerant storage tank (41). The above components and the cooling pipe (43) arranged in the clean liquid tank (3) are connected in sequence through connecting pipes to form a one-way closed-loop refrigeration circuit. Wherein: the inlet end of the cooling pipe (43) is connected to the expansion valve (46), the outlet end is connected to the inlet of the refrigerant storage tank (41), and the outlet of the refrigerant storage tank (41) is connected to the suction end of the compressor (42).

3. An integrated filtration device with cooling function according to claim 2, characterized in that, The cooling pipe (43) extends in a curved manner within the clean liquid tank (3).

4. An integrated filtration device with cooling function according to claim 2, characterized in that, The condenser (44) is disposed on top of the housing (6).

5. An integrated filtration device with cooling function according to claim 2, characterized in that, The compressor (42) and the refrigerant tank (41) are placed above the clean liquid tank (3), the condenser (44) is placed above the filter assembly (2), and the filter (45) and the expansion valve (46) are placed on the pipeline connecting the condenser (44) and the cooling pipe (43).

6. An integrated filtration device with cooling function according to claim 1, characterized in that, The cooling fan (5) is installed on the top wall of the housing (6) and vertically covers the heat dissipation surface of the condenser (44) directly above it.

7. An integrated filter device with cooling function according to claim 1, characterized in that, The filter component (2) includes: A filter pump (21) is used to draw grinding fluid; The filter tank (22) is connected to the filter pump (21) and the clean liquid tank (3) respectively. The filter tank (22) is used to filter the grinding fluid drawn out by the filter pump (21) and guide it into the clean liquid tank (3).

8. An integrated filtration device with cooling function according to claim 7, characterized in that, The filter tank (22) is provided with a filter inlet connected to the filter pump (21) and a filter outlet connected to the clean liquid tank (3).

9. An integrated filtration device with cooling function according to any one of claims 1 to 7, characterized in that, Also includes: A temperature detector (7) is installed inside the clean liquid tank (3) and is connected to the cooling assembly (4) via an electronic control unit (61). The temperature detector (7) is used to detect the temperature inside the clean liquid tank (3).

10. An integrated filtration device with cooling function according to claim 7, characterized in that, Also includes: A liquid supply pump (8) is connected to the clean liquid tank (3) to inject the cooled grinding fluid in the clean liquid tank (3) into the machine tool; And / or, The dirty liquid tank (1) has a dirty liquid inlet, which is used to communicate with the grinding fluid outlet of the machine tool. The filter pump (21) is connected to the dirty liquid tank (1) to draw the grinding fluid in the dirty liquid tank (1).

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