Suction filter device

Abstract

A suction filtration device (101, 102, 103) according to an embodiment of the present invention comprises: a container (1) for storing a liquid (w1); a filter (6) that is installed in a drain port of the container (1) and filters solid matter included in the liquid (w1); a suction pump (P1) that suctions the liquid (w1); a pipe line (L1) that directly or indirectly connects the drain port and a suction port of the suction pump (P1); detection units (4, 7) that detect the inflow of air into the pipe line (L1); and a control unit (5) whereby it is determined that filtration of the liquid (w1) in the container (1) has ended when the inflow of air into the pipe line (L1) is detected.

Description

suction filtration device

[0001] An embodiment of the present invention relates to a suction filtering device that suction filters a liquid stored in a container and collects solid matter in the liquid.

[0002] For example, suction filtration devices are used to extract nucleic acids, which are genetic material, from microorganisms and viruses associated with infectious diseases contained in sewage. Suction filtration devices are equipped with a container for storing liquids such as sewage, and by filtering the sewage stored in the container using a filter, solid matter including proteins, microorganisms, nucleic acids, etc. is collected.

[0003] Specifically, a filter is installed at the drain outlet of a container storing sewage, and the drain outlet is connected to the suction port of a suction pump via a pipe. The suction pump is driven to create negative pressure in the pipe, and the sewage in the container is sucked and filtered, allowing solid matter adhering to the filter to be collected, and ultimately proteins, microorganisms, nucleic acids, etc. contained in the solid matter to be collected.

[0004] Japanese Patent Application Laid-Open No. 2018-155697

[0005] In conventional suction filtration devices, if the suction pump continues to operate after the suction filtration of the liquid in the container is completed, the solid matter adhering to the filter may dry out, making it impossible to use as a sample. Therefore, once the suction filtration of the liquid is completed, it is desirable to quickly close the pipeline and stop the suction pump.

[0006] Furthermore, conventional suction filtration devices do not have a function to detect when all of the liquid in the container has been filtered. Therefore, the operator visually monitors the amount of liquid remaining in the container and stops the suction pump when all of the liquid has been filtered. However, the time required for suction filtration varies depending on the amount of liquid stored in the container and the amount of solids contained in the liquid. This makes it difficult to determine when suction filtration will finish, making it difficult for the operator to stop the suction pump in a timely manner to coincide with the completion of suction filtration.

[0007] The problem to be solved by the present invention is to provide a suction filtration device that can quickly detect the end of suction filtration when filtration of all the liquid stored in the container has been completed.

[0008] A suction filtration device according to one embodiment includes a container, a filter, a pump, a conduit, a detection unit, and a control unit. The container stores a liquid. The filter is installed at the drain outlet of the container and filters out solid matter contained in the liquid. The pump sucks the liquid. The conduit directly or indirectly connects the drain outlet to the suction port of the pump. The detection unit detects air flowing into the conduit. The control unit determines that filtration of the liquid in the container has completed when air flowing into the conduit is detected.

[0009] A suction filtration device according to one embodiment includes a container, a filter, a pump, a conduit, a cylinder, a measuring unit, and a control unit. The container includes a lid, has a sealed structure, and stores a liquid. The filter is installed at the drain outlet of the container and filters out solids contained in the liquid. The pump sucks the liquid. The conduit directly or indirectly connects the drain outlet to the suction port of the pump. The cylinder includes a tube connected to the lid and a piston that slides in response to air pressure within the tube. The measuring unit measures the sliding position of the piston. The control unit determines that filtration of the liquid in the container has completed when the air pressure within the tube decreases and the sliding position of the piston reaches a predetermined position.

[0010] FIG. 1 is an explanatory diagram schematically showing the configuration of a suction filtration device according to a first embodiment. FIG. 2 is a flowchart showing the processing procedure of the suction filtration device according to the first embodiment. FIG. 3A is a first sub-diagram of a flowchart showing the detailed processing procedure of the filtration end determination processing shown in FIG. 2. FIG. 3B is a second sub-diagram of a flowchart showing the detailed processing procedure of the filtration end determination processing shown in FIG. 2. FIG. 3C is a third sub-diagram of a flowchart showing the detailed processing procedure of the filtration end determination processing shown in FIG. 2. FIG. 4 is an explanatory diagram schematically showing the configuration of a suction filtration device according to a modified example of the first embodiment. FIG. 5 is an explanatory diagram schematically showing the configuration of a suction filtration device according to a second embodiment. FIG. 6 is a flowchart showing the processing procedure of the suction filtration device according to the second embodiment. FIG. 7 is a flowchart showing the detailed processing procedure of the filtration end determination processing shown in FIG. 6. FIG. 8 is an explanatory diagram schematically showing the configuration of a suction filtration device according to a third embodiment. FIG. 9 is a flowchart showing the processing procedure of a suction filtration device according to the third embodiment.

[0011]

[0023] Hereinafter, embodiments will be described with reference to the drawings. (First Embodiment) Fig. 1 is an explanatory diagram showing a schematic configuration of a suction filtration device 101 according to a first embodiment. As shown in Fig. 1, the suction filtration device 101 includes a container 1, a trap bottle 2, a suction pump P1 (pump), a pressure sensor 4, a control unit 5, two solenoid valves SV1 and SV2, and pipelines L1 and L2.

[0012] The container 1 stores a liquid w1, such as sewage. A drain outlet is provided at the bottom of the container 1. The drain outlet is provided with a filter 6 for filtering solid matter (e.g., suspended matter) contained in the liquid w1. The solid matter includes, for example, microorganisms and viruses related to infectious diseases. The filter 6 is made of, for example, glass fiber, and collects the solid matter contained in the liquid w1.

[0013] The drain outlet of the container 1 is connected to the trap bottle 2 via a conduit L1. The trap bottle 2 is connected to the suction port of the suction pump P1 via a conduit L2. The conduits L1 and L2 directly or indirectly connect the drain outlet of the container 1 to the suction port of the suction pump P1. "Directly connected" refers to connecting the container 1 to the trap bottle 2 via the conduit L1, as shown in FIG. 1. "Indirectly connected" refers to connecting the container 1 to the sealed container 22 and the trap bottle 2 via the conduit L1, as shown in FIG. 4 (a modified example) described below. Two solenoid valves SV1 and SV2 are installed on the path of the conduit L1 to switch between allowing and blocking the liquid w1. The trap bottle 2 is located between the conduit L1 and the suction port of the suction pump P1 and stores the liquid w1 that has passed through the filter 6.

[0014] A pressure sensor 4 is installed in the pipe L1 between the solenoid valves SV1 and SV2. The pressure sensor 4 measures the pressure in the pipe L1. The pressure sensor 4 outputs the measured pressure data to the control unit 5. Based on the pressure data, the control unit 5 detects that air has flowed into the pipe L1 based on the following two conditions (A) and (B), i.e., based on a predetermined pressure change.

[0015] Condition (A): When the suction pump P1 completes suction of the liquid w1, the pressure in the conduit L1 immediately rises, changing from negative to positive pressure, and then drops back to negative pressure. This pressure change is detected to determine the completion of suction filtration. Condition (B): When the suction pump P1 completes suction of the liquid w1, there is no sudden change in pressure at the time of completion, but the pressure in the conduit L1 gradually rises and shifts to positive pressure. This pressure change is detected to determine the completion of suction filtration.

[0016] The control unit 5 determines that the suction is complete when one of the above conditions (A) and (B) is met.

[0017] The suction port of the suction pump P1 is connected to the discharge port of the container 1 via a conduit L2, a trap bottle 2, and a conduit L1. By driving the suction pump P1, the liquid w1 stored in the container 1 can be sucked. By sucking the liquid w1 with the suction pump P1, solids contained in the liquid w1 can be filtered by the filter 6, and the filtered liquid w1 can be stored in the trap bottle 2.

[0018] The control unit 5 controls the operation of the suction pump P1 and the opening and closing of the solenoid valves SV1 and SV2. The control unit 5 determines whether air has flowed into the conduit L1 based on the pressure in the conduit L1 detected by the pressure sensor 4. That is, after the suction pump P1 has completely filtered the liquid w1 in the container 1, air then flows into the conduit L1. The inflow of air changes the pressure in the conduit L1 as indicated by the above-described condition (A) or condition (B). The control unit 5 detects the inflow of air by observing a series of pressure changes based on the measurement results of the pressure sensor 4. That is, the control unit 5 functions as a determination unit that determines that the filtration of the liquid w1 in the container 1 has ended when the inflow of air into the conduit L1 is detected. The pressure sensor 4 functions as a detection unit that detects the inflow of air into the conduit L1.

[0019] The control unit 5 determines that the filtration of the liquid w1 has ended when it detects that air has flowed into the pipeline L1. The control unit 5 stops the suction pump P1 when the filtration of the liquid w1 stored in the container 1 has ended. That is, after the filtration of the liquid w1 has ended, the control unit 5 closes the solenoid valve SV2 to prevent solid matter (e.g., suspended matter) adhering to the filter 6 from being exposed to the airflow. The control unit 5 notifies the user by displaying the end of filtration on a display (not shown) or the like.

[0020] Next, the operation of the suction filtration device 101 according to the first embodiment will be described with reference to the flowcharts shown in Figures 2 and 3A to 3C. As an initial setting, a liquid w1 (e.g., sewage) to be inspected is stored in the container 1. In addition, a filter 6 for filtering out solid matter is installed at the drain outlet of the container 1.

[0021] First, in step S1 of FIG. 2, the control unit 5 starts the suction pump P1.

[0022] In step S2, the control unit 5 opens the solenoid valves SV1 and SV2, causing the suction pump P1 to start suctioning the liquid w1.

[0023] In step S3, the control unit 5 starts the suction pump P1 and then waits for a predetermined time (for example, 200 msec).

[0024] In step S4, the control unit 5 starts acquiring the pressure value detected by the pressure sensor 4. In this process, the control unit 5 acquires the pressure value from the pressure sensor 4, for example, every time 200 msec has elapsed.

[0025] In step S5, the control unit 5 executes a filtering end determination process. The filtering end determination process will be described in detail below with reference to the flowcharts shown in Figures 3A to 3C.

[0026] In step S51 of FIG. 3A, the control unit 5 waits for an arbitrary interval time (for example, 200 msec) to elapse.

[0027] In step S52 , the control unit 5 acquires an AD converted value of the pressure detected by the pressure sensor 4 .

[0028] In step S53, the control unit 5 obtains the average value AV, maximum value Pmax, and minimum value Pmin of each AD converted value from the most recent 20 AD converted pressure values. At this time, the average value AD from the first measurement is used as the peak hold average value, and from the second measurement onwards, the average value AV(t-1) from the previous measurement is compared with the average value AV(t) of the current measurement, and if "AV(t) > AV(t-1)", the peak hold average value is updated. In other words, the maximum average value AV after detection by the pressure sensor 4 began is saved as the peak hold average value.

[0029] In step S54, the control unit 5 compares the average value AV(t-1) from the previous measurement with the average value AV(t) of the current measurement. That is, it determines whether or not "AV(t) < AV(t-1)". If "AV(t) < AV(t-1)" is true (S54; YES), the process proceeds to step S55. If "AV(t) < AV(t-1)" is not true (S54; NO), the process proceeds to step S56. That is, when the average value AV of the AD converted values ​​is decreasing, it indicates that the pressure in the conduit L1 is changing from negative pressure to positive pressure, and when it is increasing, it indicates that the pressure in the conduit L1 is changing from positive pressure to negative pressure.

[0030] In step S55, the control unit 5 counts up the down count value CTd to set it to "CTd = CTd + 1." Thereafter, the process proceeds to step S57 shown in FIG. 3B.

[0031] In step S56, the control unit 5 resets the down count value CTd. Then, the process proceeds to step S57. That is, when the pressure detected by the pressure sensor 4 increases from negative pressure to positive pressure and the AD conversion value is on a downward trend, the control unit 5 counts up the down count value CTd. When the downward trend ends, the control unit 5 resets the down count value CTd.

[0032] In step S57, the control unit 5 determines whether the decrease count value CTd is 5. "CTd = 5" is a preset threshold value, and other values ​​may be used. If "CTd = 5" is true (S57; YES), the process proceeds to step S58. If "CTd = 5" is not true (S57; NO), the process proceeds to step S59. That is, as indicated in the above-mentioned condition (A), when the suction of the liquid w1 is completed, the pressure in the conduit L1 may suddenly increase (i.e., the AD conversion value suddenly decreases), and the process of step S57 determines whether this pressure increase has occurred.

[0033] In step S58, the control unit 5 determines whether the value obtained by subtracting the minimum value from the peak hold (PH) average value exceeds a predetermined threshold value. That is, the control unit 5 determines whether "(PH average value) - (minimum value) > threshold value" holds. If "(PH average value) - (minimum value) > threshold value" holds (S58; YES), the process proceeds to step S61; if "(PH average value) - (minimum value) > threshold value" does not hold (S58; NO), the process proceeds to step S66.

[0034] In step S59, the control unit 5 determines whether the value obtained by subtracting the minimum value from the peak hold (PH) average value exceeds a predetermined threshold value. That is, the control unit 5 determines whether "(PH average value) - (minimum value) > threshold value" holds. If "(PH average value) - (minimum value) > threshold value" holds (S59; YES), the process proceeds to step S60, and if "(PH average value) - (minimum value) > threshold value" does not hold (S59; NO), the process proceeds to step S66. That is, it is confirmed that "(PH average value) - (minimum value) > threshold value" holds.

[0035] In step S60, the control unit 5 determines whether the time at which the minimum value occurred is later than the time at which the maximum value occurred. If the time at which the minimum value occurred is later than the time at which the maximum value occurred (S60; YES), the process proceeds to step S61. If the time at which the minimum value occurred is not later than the time at which the maximum value occurred (S60; NO), the process proceeds to step S66. In this process, based on the AD conversion values ​​from the most recent 20 measurements, it is confirmed that the AD conversion values ​​are on a downward trend, i.e., that the pressure in the conduit L1 is on an upward trend. In other words, the fact that the minimum value occurs after the maximum value means that the AD conversion value is decreasing and the pressure in the conduit L1 is increasing.

[0036] In step S61, the control unit 5 determines whether the number of times that the value obtained by subtracting the minimum value from the peak hold (PH) average value has exceeded the predetermined threshold is the first time. If it is the first time (S61; YES), the process proceeds to step S63, and if it is not the first time (S61; NO), the process proceeds to step S62.

[0037] In step S62, the control unit 5 determines whether or not the minimum value of the AD conversion value of the pressure sensor 4 has been updated. If it has been updated (S62; YES), the process proceeds to step S64, and if it has not been updated (S62; NO), the process proceeds to step S65.

[0038] In step S63, the control unit 5 determines that suction filtration of the liquid w1 has ended. Then, the process proceeds to step S66 shown in FIG. 3C . That is, if the down count value CTd has reached five and the difference between the peak hold average value and the minimum value has exceeded the threshold value, the control unit 5 determines that suction filtration has ended if this is the first time. Furthermore, even if the down count has not reached five, if the difference between the peak hold average value and the minimum value has exceeded the threshold value and the maximum value of the AD conversion value has occurred before (at an earlier time than) the minimum value, the control unit 5 determines that suction filtration has ended if this is the first time.

[0039] In step S64, the control unit 5 updates the minimum value of the AD converted value of the pressure sensor 4. Thereafter, the process proceeds to step S66.

[0040] In step S65, the control unit 5 increments the upper limit count value CTu to "CTu = Ctu + 1." Then, the process proceeds to step S66.

[0041] In step S66, the control unit 5 determines whether or not it has been determined in the processing of step S63 that suction filtration has been completed. If suction filtration has been completed (S66; YES), the processing proceeds to step S67. If suction filtration has not been completed (S66; NO), the processing proceeds to step S68. That is, the control unit 5 determines that filtration has been completed when the "pH average value - minimum value" exceeds the threshold value and the AD conversion value is on a downward trend (i.e., the pressure is on an upward trend).

[0042] In step S67, the control unit 5 counts the number of times the filtration is completed and then proceeds to step S68.

[0043] In step S68, the control unit 5 determines whether the number of passes has reached a specified number (for example, 20 times). If the specified number has been reached (S68; YES), the process proceeds to step S70, and if the specified number has not been reached (S68; NO), the process proceeds to step S69.

[0044] In step S69, the control unit 5 determines whether or not the upper limit count value CTu = 5. If "CTu = 5" (S69; YES), the process proceeds to step S70, and if "CTu = 5" is not true (S69; NO), the process proceeds to step S71.

[0045] In step S70, the control unit 5 determines whether the minimum filtering time has elapsed. The minimum filtering time is a time preset by the user. If the minimum filtering time has elapsed (S70; YES), the process proceeds to step S72. If the minimum filtering time has not elapsed (S70; NO), the process proceeds to step S71.

[0046] In step S71, the control unit 5 determines whether or not a timeout has occurred. If a timeout has occurred (S71; YES), the suction filtration process is terminated due to the timeout. If a timeout has not occurred (S71; NO), the process returns to step S51 in FIG. 3A.

[0047] In step S72, the control unit 5 determines whether a timeout has occurred. If a timeout has occurred (S72; YES), the suction filtration process is terminated. If a timeout has not occurred (S72; NO), the suction filtration process is terminated normally. Thereafter, the process proceeds to step S6 in FIG. 2.

[0048] That is, the control unit 5 determines that filtration is complete in the process of step S63, and if this determination is made 20 times consecutively in the process of step S68, it determines that suction filtration has been completed normally for all of the liquid w1 in the container 1. Furthermore, even if the filtration completion determination is made less than 20 times, the control unit 5 determines that suction filtration has been completed normally if the count value CTu, which indicates a tendency for pressure to rise, reaches 5 times in step S69.

[0049] In step S6 of FIG. 2, the control unit 5 closes the solenoid valves SV1 and SV2.

[0050] In step S7, the control unit 5 stops the suction pump P1. When the filtration of the liquid w1 stored in the container 1 is thus completed and the liquid w1 in the container 1 is depleted, the control unit 5 closes the solenoid valve SV2 and stops the suction pump P1, thereby completing the filtration.

[0051] In this way, in the suction filtration device 101 according to the first embodiment, by driving the suction pump P1, solid matter in the liquid w1 is filtered, and nucleic acids, which are genetic material, can be extracted from, for example, infectious disease-related microorganisms and viruses contained in the solid matter. Furthermore, when filtration of the liquid w1 stored in the container 1 is completed and the liquid w1 in the container 1 is depleted, air flows into the conduit L1, causing a drop in pressure. The control unit 5 detects the change in pressure and determines the end of filtration. Therefore, when filtration of the liquid w1 is completed, that fact can be detected immediately, i.e., quickly, and the solenoid valves SV1 and SV2 can be closed and the suction pump P1 can be stopped. This prevents the solid matter filtered by the filter 6 from being exposed to airflow after filtration is completed, preventing the solid matter from drying out.

[0052] (Modification of First Embodiment) Next, a modification of the first embodiment will be described. Fig. 4 is an explanatory diagram schematically showing the configuration of a suction filtration device 101A according to a modification of the first embodiment. As shown in Fig. 4, the suction filtration device 101A differs from the suction filtration device 101 shown in Fig. 1 in that a sealed container 22 is installed between the container 1 and the pipeline L1.

[0053] A filtrate collection container 21 is provided inside the sealed container 22. The liquid w1 flowing out from the container 1 via the filter 6 is introduced into the sealed container 22 and poured into the filtrate collection container 21. When the liquid w1 poured into the filtrate collection container 21 overflows, this liquid w1 flows from the sealed container 22 into the line L1 and is introduced into the trap bottle 2 via the solenoid valves SV1 and SV2, as in the first embodiment described above.

[0054] In the suction filtration device 101A according to the modified example, as in the first embodiment described above, the completion of filtration of the liquid w1 can be detected immediately, i.e., quickly, and the solenoid valves SV1 and SV2 can be closed and the suction pump P1 can be stopped. This prevents the solid matter filtered by the filter 6 from being exposed to airflow after filtration is completed, thereby preventing the solid matter from drying out. Furthermore, the filtrate obtained by filtering the liquid w1 through the filter 6 can be collected in the filtrate collection container 21.

[0055] (Description of Second Embodiment) Next, a second embodiment will be described. Fig. 5 is an explanatory diagram schematically showing the configuration of a suction filtration device 102 according to the second embodiment. As shown in Fig. 5, the suction filtration device 102 includes a container 1, a trap bottle 2, a suction pump P1, an airflow sensor (airflow detection unit) 7, a control unit 5A, two solenoid valves SV1 and SV2, and pipelines L1 and L2.

[0056] The container 1, trap bottle 2, suction pump P1, two solenoid valves SV1 and SV2, and pipelines L1 and L2 have the same configuration as in the first embodiment, so they are denoted by the same reference numerals and their description will be omitted.

[0057] The airflow sensor 7 is installed in the conduit L1 between the two solenoid valves SV1 and SV2. The airflow sensor 7 detects the flow speed of air flowing through the conduit L1. The airflow sensor 7 is equipped with, for example, a propeller and measures the rotation speed of the propeller. The airflow sensor 7 detects that air has flowed into the conduit L1 when the airflow speed exceeds a predetermined upper speed limit. The airflow sensor 7 outputs data on the measured rotation speed to the control unit 5A.

[0058] The control unit 5A controls the operation of the suction pump P1 and the opening and closing of the solenoid valves SV1 and SV2. The control unit 5A determines whether air has flowed into the conduit L1 based on the air flow velocity in the conduit L1 detected by the airflow sensor 7. That is, after the suction pump P1 has completely filtered the liquid w1 in the container 1, air then flows into the conduit L1. The inflow of air increases the air flow velocity in the conduit L1. The control unit 5A determines whether air has flowed into the conduit L1 based on the air flow velocity detected by the airflow sensor 7. That is, the control unit 5A functions as a determination unit that determines that the filtration of the liquid w1 in the container 1 has ended when the inflow of air into the conduit L1 is detected. The airflow sensor 7 functions as a detection unit that detects the inflow of air into the conduit L1.

[0059] The control unit 5A determines that filtration of the liquid w1 has ended when it detects that air has flowed into the conduit L1. When filtration of the liquid w1 stored in the container 1 has ended, the control unit 5A closes the solenoid valve SV2 and stops the suction pump P1. That is, after filtration of the liquid w1 has ended, the control unit 5A closes the solenoid valve SV2 and stops the suction pump P1, thereby preventing solid matter (e.g., suspended matter) adhering to the filter 6 from being exposed to the airflow. The control unit 5A notifies the user by displaying the end of filtration on a display (not shown) or the like.

[0060] Next, the operation of the suction filtration device 102 according to the second embodiment will be described with reference to the flowcharts shown in Figures 6 and 7. As an initial setting, a liquid w1 to be inspected (e.g., sewage) is stored in the container 1. In addition, a filter 6 for filtering solid matter is installed at the drain outlet of the container 1.

[0061] In step S101 of FIG. 6, the control unit 5A starts the suction pump P1.

[0062] In step S102, the control unit 5A opens the solenoid valves SV1 and SV2, causing the suction pump P1 to start suctioning the liquid w1.

[0063] In step S103, the control unit 5A waits for a predetermined time (for example, a time until the airflow inside the pipe becomes stable) after starting the suction pump P1.

[0064] In step S104, the control unit 5A starts acquiring the air flow velocity detected by the airflow sensor 7. In this process, the control unit 5A acquires the air flow velocity in the conduit L1 every time an arbitrary interval time (for example, 200 msec) elapses.

[0065] In step S105, the control unit 5A executes a filtering end determination process. The filtering end determination process will be described in detail below with reference to the flowchart shown in FIG.

[0066] 7, the control unit 5A acquires the air flow velocity (A / D converted value) detected by the airflow sensor 7 at each time interval elapses, and acquires the moving average value AV, maximum moving average value Vmax, and minimum moving average value Vmin from the flow velocity for a specified number of times (e.g., 20 times). At this time, the maximum moving average value Vmax is saved as a peak hold value. That is, the maximum moving average value of the flow velocity detected after detection by the airflow sensor 7 begins is saved as Vmax.

[0067] In step S152, control unit 5A resets the count value CT of the counter.

[0068] In step S153, the control unit 5A compares the moving average value AV(t) of the flow velocity for a specified number of times (for example, 20 times) calculated in the current calculation with the moving average value AV(t-1) calculated in the previous calculation, and determines whether or not "AV(t) > AV(t-1)". If "AV(t) > AV(t-1)" is true (S153; YES), the process proceeds to step S154, and if "AV(t) > AV(t-1)" is not true (S153; NO), the process returns to step S152.

[0069] In step S154, the control unit 5 increments the count value CT of the counter to "CT=CT+1".

[0070] In step S155, the control unit 5 determines whether the count value CT has reached the threshold value CTth. If the count value CT has reached the threshold value CTth (S155; YES), the process proceeds to step S156. If the count value CT has not reached the threshold value CTth (S155; NO), the process returns to step S153.

[0071] In step S156, the control unit 5A calculates the difference DT between the maximum moving average value Vmax and the minimum moving average value Vmin of the flow velocity. That is, the control unit 5A calculates "DT=Vmax-Vmin."

[0072] In step S157, the control unit 5A determines whether the difference DT is equal to or greater than a predetermined threshold value DTth. If DT≧DTth holds (YES in step S157), the process proceeds to step S158. If DT≧DTth does not hold (NO in step S157), the process returns to step S156.

[0073] In step S158, the control unit 5A determines that the suction filtration of the liquid w1 has ended.

[0074] In step S106 of FIG. 6, the control unit 5A closes the solenoid valves SV1 and SV2.

[0075] In step S107, the control unit 5A stops the suction pump P1. When the filtration of the liquid w1 stored in the container 1 is thus completed and the liquid w1 in the container 1 is depleted, the control unit 5A closes the solenoid valve SV2 and stops the suction pump P1, thereby completing the filtration.

[0076] In this way, in the suction filtration device 102 of the second embodiment, by driving the suction pump P1, solid matter in the liquid w1 can be filtered, and nucleic acids, which are genetic material, can be extracted from, for example, microorganisms and viruses related to infectious diseases contained in the solid matter.

[0077] Furthermore, when the filtration of the liquid w1 stored in the container 1 is completed and the liquid w1 in the container 1 is depleted, air flows into the conduit L1, increasing the air flow rate in the conduit L1. The control unit 5A detects the increase in flow rate and determines the end of filtration. Therefore, when the filtration of the liquid w1 is completed, the control unit 5A can immediately, i.e., quickly, detect this, close the solenoid valves SV1 and SV2, and stop the suction pump P1. This prevents the solid matter filtered by the filter 6 from being exposed to the airflow after filtration is completed, thereby preventing the solid matter from drying out. Furthermore, the second embodiment may also be configured to include the sealed container 22 and filtrate collection container 21 shown in FIG. 4, as in the modified example of the first embodiment described above. This allows the filtrate to be collected.

[0078] 8 is an explanatory diagram schematically illustrating the configuration of a suction filtration device 103 according to a third embodiment. As shown in Fig. 8, the suction filtration device 103 includes a container 1, a trap bottle 2, a suction pump P1, a cylinder 11, a position sensor 12, a control unit 5B, a solenoid valve SV11 that switches between allowing and sealing the liquid w1, and pipelines L11, L12, and L13.

[0079] The container 1 stores a liquid w1, such as sewage, in the same manner as in the first embodiment described above. A filter 6 is provided at a drain outlet on the bottom of the container 1 to filter out solid matter contained in the liquid w1. The solid matter includes, for example, microorganisms and viruses related to infectious diseases. The filter 6 is made of, for example, glass fiber, and collects the solid matter contained in the liquid w1.

[0080] A lid 1A is provided on the upper opening of the container 1. By attaching the lid 1A to the container 1, the interior of the container 1 can be sealed, preventing the intrusion of outside air. The drain outlet of the container 1 is connected to a trap bottle 2 via a pipe L11. The trap bottle 2 is connected to a suction port of a suction pump P1 via a pipe L12. An electromagnetic valve SV11 is installed on the path of the pipe L11. The pipes L11 and L12 directly or indirectly connect the drain outlet of the container 1 to the suction port of the suction pump P1.

[0081] One end of a conduit L13 is connected to the lid 1A of the container 1. The other end of the conduit L13 is connected to a tube 11A of the cylinder 11. A piston 11B of the cylinder 11 slides in response to the pressure inside the tube 11A. That is, the cylinder 11 has a tube 11A and a piston 11B, and the tube 11A is connected to the lid 1A of the container 1. The piston 11B slides in response to the air pressure inside the tube 11A. Specifically, when the pressure inside the tube 11A is high, the piston 11B slides in the expanding direction (downward in FIG. 8 ), and when the pressure inside the tube 11A is low, the piston 11B slides in the contracting direction (upward in FIG. 8 ).

[0082] The position sensor 12 detects the position of the piston 11B. When the air pressure inside the container 1 decreases and the piston 11B slides in the contracting direction and reaches a predetermined position, the position sensor 12 outputs a detection signal of the decrease in air pressure to the control unit 5B. In other words, the position sensor 12 functions as a measurement unit that measures the slide position of the piston 11B.

[0083] The suction port of the suction pump P1 is connected to the discharge port of the container 1 via a conduit L12, a trap bottle 2, and a conduit L11. By driving the suction pump P1, the liquid w1 stored in the container 1 can be sucked. By sucking the liquid w1 with the suction pump P1, solid matter can be filtered out by the filter 6 contained in the liquid w1. The filtered liquid w1 can be stored in the trap bottle 2.

[0084] The control unit 5B controls the operation of the suction pump P1 and the opening and closing of the solenoid valve SV11. The control unit 5B determines whether or not the filtration of the liquid w1 stored in the container 1 has been completed based on the detection signal of the drop in air pressure output from the position sensor 12. That is, when the liquid w1 is stored in the container 1, the pressure in the container 1 is high. When the filtration of the liquid w1 in the container 1 has been completed, the suction pump P1 sucks air from the container 1, thereby reducing the pressure in the container 1 and, ultimately, the pressure in the tube 11A. As a result, the piston 11B slides in the contracting direction, and the position sensor 12 detects that it has reached a predetermined position. That is, the control unit 5B functions as a determination unit that determines that the filtration of the liquid w1 in the container 1 has been completed when the air pressure in the tube 11A drops and the sliding position of the piston 11B reaches a predetermined position.

[0085] The control unit 5B determines that filtration of the liquid w1 has been completed based on the detection signal of the drop in air pressure. When filtration of the liquid w1 stored in the container 1 has been completed, the control unit 5B stops the suction pump P1. That is, after filtration of the liquid w1 has been completed, the control unit 5B closes the solenoid valve SV11 and stops the suction pump P1, thereby preventing solid matter (e.g., suspended matter) adhering to the filter 6 from being exposed to the airflow. The control unit 5B notifies the user by displaying the completion of filtration on a display (not shown) or the like.

[0086] Next, the operation of the suction filtration device 103 according to the third embodiment will be described with reference to the flowchart shown in Fig. 9. As an initial setting, a liquid w1 to be inspected (e.g., sewage) is stored in the container 1. In addition, a filter 6 for filtering out solid matter is installed at the drain outlet of the container 1.

[0087] First, in step S201 of FIG. 9, the control unit 5B starts the suction pump P1.

[0088] In step S202, the control unit 5B opens the electromagnetic valve SV11, causing the suction pump P1 to start suctioning the liquid w1.

[0089] In step S203, the control unit 5B starts the suction pump P1 and then waits for, for example, 200 msec.

[0090] In step S204, the control unit 5B starts detecting the position of the piston 11B in the cylinder 11. Specifically, the control unit 5B starts detecting the position of the piston 11B using the position sensor 12 installed near the piston 11B. In this process, the control unit 5B acquires the position of the piston 11B from the position sensor 12, for example, every time 200 msec has elapsed.

[0091] In step S205, the control unit 5B determines whether the position of the piston 11B has reached a predetermined position. If the predetermined position has been reached (S205; YES), the control unit 5B determines that filtration of all of the liquid w1 stored in the container 1 has been completed. If the predetermined position has not been reached (S205; NO), the control unit 5B repeats the processing of step S205.

[0092] In step S207, the control unit 5B closes the solenoid valve SV11.

[0093] In step S208, the control unit 5B stops the suction pump P1. When the filtration of the liquid w1 stored in the container 1 is thus completed and the liquid w1 in the container 1 is depleted, the control unit 5B closes the solenoid valve SV11 and stops the suction pump P1, thereby completing the filtration.

[0094] In this way, in the suction filtration device 103 according to the third embodiment, by driving the suction pump P1, solid matter in the liquid w1 can be filtered, and proteins such as RNA contained in the solid matter can be collected.

[0095] Furthermore, when filtration of the liquid w1 stored in the container 1 is completed and the liquid w1 in the container 1 is depleted, the pressure in the tube 11A of the cylinder 11 decreases, causing the piston 11B to slide to a predetermined position. Therefore, the end of filtration can be detected immediately, i.e., quickly, and the solenoid valve SV11 can be closed and the suction pump P1 can be stopped. This prevents the solid matter filtered by the filter 6 from being exposed to airflow after filtration is completed, thereby preventing the solid matter from drying out. Furthermore, the third embodiment may also be configured to include the sealed container 22 and filtrate collection container 21 shown in FIG. 4, as in the modified example of the first embodiment described above. This allows the filtrate to be collected.

[0096] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

Claims

1. A suction filtration device comprising: a container for storing liquid; a filter installed at the drain outlet of the container for filtering out solid matter contained in the liquid; a pump for sucking the liquid; a pipeline directly or indirectly connecting the drain outlet and the suction port of the pump; a detection unit for detecting air flowing into the pipeline; and a control unit for determining that filtration of the liquid in the container has been completed when air flowing into the pipeline is detected.

2. The suction filtration device according to claim 1, wherein the detection unit includes a pressure sensor that measures the pressure in the pipeline, and the pressure sensor monitors pressure changes in the pipeline and detects that air has flowed into the pipeline when a predetermined pressure change is detected.

3. The suction filtration device according to claim 1, wherein the detection unit includes an airflow sensor that detects the airflow velocity in the duct, and the airflow sensor detects that air has flowed into the duct when the detected airflow velocity exceeds a predetermined upper limit velocity.

4. A suction filtration device according to any one of claims 1 to 3, further comprising a trap bottle disposed between the pipeline and the suction port of the pump, for containing the liquid that has passed through the filter.

5. The suction filtering device according to claim 1, further comprising valves provided in each of the pipelines on the upstream and downstream sides of the detection unit for switching between allowing and blocking the liquid.

6. A suction filtration device comprising: a container having a lid, a sealed structure, and for storing a liquid; a filter installed at the drain outlet of the container and for filtering out solid matter contained in the liquid; a pump for sucking the liquid; a pipeline directly or indirectly connecting the drain outlet and the suction port of the pump; a cylinder including a tube connected to the lid and a piston that slides in accordance with the air pressure inside the tube; a measuring unit that measures the sliding position of the piston; and a control unit that determines that filtration of the liquid inside the container has been completed when the air pressure inside the tube decreases and the sliding position of the piston reaches a predetermined position.

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