Screw press outer cylinder screen cleaning method

Abstract

To provide a screw press external cylinder screen washing method that eliminates clogging at a screen bottom by increasing washing strength when a screen bottom surface passes a cleaning fluid supply zone during washing of an external cylinder screen.SOLUTION: In a screw press having an external cylinder screen 5 in which a washing pipe 13 is extended along an axial direction of a screw shaft 7 and which passes a washing fluid supply zone where a washing fluid is supplied toward a screen surface while rotating, a rotation angle θ of the washing fluid supply zone that is previously calculated in a rotation direction of the screen from a screen bottom surface 28 and a rotational speed of the external cylinder screen 5 during washing the external cylinder screen are set, a rotation angle θ of the screen bottom surface 28 from rotation start of the external cylinder screen 5 is measured, the screen bottom surface 28 rotates by θ / 360, and a washing strength is increased only while passing the washing fluid supply zone, whereby clogging at the screen bottom surface is eliminated, and the whole area of the screen is evenly washed.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a method for cleaning an outer cylinder screen of a screw press, and more particularly to a method for cleaning an outer cylinder screen of a screw press that can efficiently eliminate local clogging occurring on the bottom surface of the screen.

Background Art

[0002] Conventionally, screw presses for concentrating and dewatering organic sludge such as sewage, night soil, or food production and processing wastewater are generally known. For example, Patent Document 1 discloses a screw press in which a screw shaft wrapped with spiral blades is rotatably installed in a cylindrical outer cylinder screen having a large number of fine pores, and the raw liquid supplied to one end of the screw shaft is filtered and dewatered while being conveyed toward the other end. The screw press disclosed in Patent Document 1 is a technology that uses a single drive device to rotate the screw shaft and the screen, and during dewatering operation, only the screw shaft rotates counterclockwise, and during screen cleaning, the mechanism is such that the screen rotates together with the clockwise rotating screw shaft.

[0003] Further, Patent Document 2 discloses a cleaning mechanism for a screw press, which describes a technology that, when the load on the screw shaft increases during dewatering operation, determines that the screen drum is clogged and injects high-pressure fluid onto the screen drum to eliminate the clogging.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventionally, filtration and dewatering in screw presses are performed across the entire screen surface, but gravity is generated in addition to internal pressure as part of the filtration pressure. In particular, the bottom surface of the screen, which is subjected to internal pressure and gravity, has the problem of being prone to clogging of the filtration surface. As shown in Figure 3, the screw press of Patent Document 1 has a configuration in which the screen stops when a ratchet pawl provided on the end plate at the other end of the screen engages with a stopper provided on the end plate of the screen. Since there is only one stopper to engage the ratchet pawl, the position of the bottom surface of the filtration when the screen stops is the same each time. Because the dewatering operation is repeatedly performed in this state, localized clogging occurs on the bottom surface of the screen.

[0006] Patent Document 2 describes a technology that installs an injection nozzle above the compression zone at the downstream end of the screen drum, where clogging is likely to occur, and injects high-pressure fluid when a load on the feed shaft is detected to clear clogging in the compression zone. However, because the injection nozzle is installed only above the compression zone, it cannot clear clogging in the filtration and dewatering zone at the upstream end of the screen drum. Since the dewatering operation is performed without clearing clogging across the entire screen, it leads to a decrease in dewatering efficiency. Furthermore, this technology is aimed at clearing clogging in the compression zone, and does not describe or suggest anything regarding clearing clogging at the bottom of the screen.

[0007] The present invention provides a method for cleaning the outer cylinder screen of a screw press, which can eliminate clogging of the screen bottom by increasing the cleaning intensity as the screen bottom passes through the cleaning fluid supply zone during outer cylinder screen cleaning, thereby intensively cleaning the screen bottom. [Means for solving the problem]

[0008] The present invention relates to a screw press having a cleaning pipe extending along the axial direction of the screw shaft and an outer cylinder screen that rotates and passes through a cleaning fluid supply zone through which cleaning fluid is supplied toward the screen surface. The invention sets the rotation angle θ of the cleaning fluid supply zone calculated in advance from the bottom surface of the screen in the direction of screen rotation, and the rotation speed of the outer cylinder screen during outer cylinder screen cleaning. The rotation angle θ of the bottom surface of the screen is measured from the start of rotation of the outer cylinder screen, and the cleaning intensity is increased only while the bottom surface of the screen rotates θ / 360 and passes through the cleaning fluid supply zone, thereby enabling concentrated cleaning of the bottom surface of the screen, which is prone to clogging.

[0009] The rotation angle θ is measured by calculation based on the elapsed time since the start of rotation of the outer cylinder screen, or by calculation based on the detection result of the position detection means. This allows us to measure the rotation angle θ.

[0010] The cleaning intensity is achieved by changing at least one of the following: the rotation speed of the outer cylinder screen or the method of supplying the cleaning fluid, which allows for concentrated cleaning of the screen bottom surface.

[0011] The aforementioned position The detection means includes at least one of the following: a non-contact sensor that irradiates light onto a detection unit installed on the bottom surface of the screen; a contact sensor that detects contact with the detection unit; and an imaging device that photographs the bottom surface of the screen. This allows the timing of when the bottom surface of the screen starts passing through the cleaning fluid supply zone and when it finishes.

[0012] The device includes a ratchet pawl that rotates integrally with the screw shaft, a stopper positioned on the rotational path of the ratchet pawl and engaging with the ratchet pawl to rotate the outer cylinder screen, a ratchet pawl that rotates integrally with the outer cylinder screen, and a stopper positioned on the rotational path of the ratchet pawl and engaging with the ratchet pawl to obstruct the rotation of the outer cylinder screen, wherein when cleaning of the outer cylinder screen begins, the ratchet pawl engages with the stopper. Locking When detected by the detection means, it is determined that the outer cylinder screen has started to rotate, allowing for the accurate calculation of the rotation angle θ.

[0013] The aforementioned LockingThe detection means is a pressure-sensitive switch installed at one or more locations between the ratchet pawl 15 and the locking surface of the stopper, or between the ratchet pawl and the locking surface of the stopper, thereby detecting when the ratchet pawl is locked to the stopper. [Effects of the Invention]

[0014] The present invention provides a method for cleaning the outer cylinder screen of a screw press. By increasing the cleaning intensity and concentrating the cleaning as the screen bottom passes through the cleaning fluid supply zone, clogging of the screen bottom can be efficiently eliminated. Since clogging of the entire screen can be eliminated, the dewatering efficiency during the next dewatering operation can be increased, and a dewatered cake with a low moisture content can be stably obtained. Consequently, the processing efficiency of downstream equipment is also improved, leading to a reduction in the overall power consumption of the equipment. Furthermore, it can be applied to all types of screw presses, both new and existing. [Brief explanation of the drawing]

[0015] [Figure 1] This is a longitudinal cross-sectional side view of the screw press according to the present invention. [Figure 2] Similarly, this is an AA cross-sectional view of a screw press. [Figure 3] Similarly, this is a partially cross-sectional side view of the starting end of the screw press in another embodiment 1. [Figure 4] Similarly, this is a cross-sectional view AA of the screw press in another embodiment 1. [Figure 5] Similarly, this is a cross-sectional view AA of the screw press in another embodiment 2. [Figure 6] Similarly, this is a schematic diagram of the stopper 16b in another embodiment 2. [Figure 7] This is also an explanatory diagram of the cleaning method for the outer cylinder screen in this embodiment. [Figure 8] This is also an explanatory diagram of the cleaning method for the outer cylinder screen in this embodiment. [Figure 9] Similarly, this is an explanatory diagram of the cleaning method for the outer cylinder screen in another embodiment 1. [Figure 10] Similarly, it is an explanatory diagram of the cleaning method for the outer cylindrical screen in the second other embodiment. [Figure 11] Similarly, it is an explanatory diagram of the cleaning method for the outer cylindrical screen in the second other embodiment. [Figure 12] Similarly, it is an explanatory diagram of the cleaning method for the outer cylindrical screen in the second other embodiment. [Mode for Carrying Out the Invention]

[0016] Figure 1 is a vertical side view of the screw press according to the present invention. In the screw press 1, an outer cylindrical screen 5 having a filtration surface on its peripheral portion is bridged between a front frame 3 and a rear frame 4 that are erected on a stand 2, and a screw shaft 7 around which screw blades 6 are wound is disposed internally. The screw shaft 7 arranged inside the outer cylindrical screen 5 has a diameter that increases in a tapered shape from the starting end side toward the terminating end side, so that the relative distance between the outer cylindrical screen 5 and the screw shaft 7 in the extending direction decreases. A sludge supply pipe 8 is connected to the front end portion of the screw shaft 7, and the supply pipe 8 communicates with a supply hole 9 of the screw shaft 7 that opens to the starting end side of the outer cylindrical screen 5.

[0017] A screw drive shaft 10 is connected to the rear end portion of the screw shaft 7, and a drive sprocket 11 is fitted onto the screw drive shaft 10. This sprocket 11 is driven by a screw drive unit (not shown) to rotate the screw shaft 7. In the present embodiment, an outer cylindrical screen drive unit (not shown) capable of forward and reverse rotation of the outer cylindrical screen 5 is installed, and the screw shaft 7 and the outer cylindrical screen 5 are configured to be rotated by the respective drive units.

[0018] The sludge supplied from the supply hole 9 flows into the filtration chamber 12 formed between the outer cylindrical screen 5 and the screw shaft 7, and then is filtered and dewatered while being conveyed from the starting end side toward the terminating end side by the screw blades 6. The conveyed sludge is caked while separating the filtrate from the outer cylindrical screen 5, and is discharged from the terminating end side as a dewatered cake.

[0019] Figure 2 is an AA cross-sectional view of the screw press according to the present invention. The screw press 1 has a rotatable screw shaft 7 inside a cylindrical outer screen 5 that can be rotated forward or backward. The screw shaft 7 rotates counterclockwise when viewed from the sludge supply side during dewatering operation. On the other hand, the outer screen 5 rotates clockwise when viewed from the sludge supply side during outer screen cleaning.

[0020] During dewatering, the outer cylinder screen 5 does not rotate, and only the screw shaft 7 rotates. Therefore, sludge filtration and dewatering are performed with the screen bottom surface 28 fixed. The screw press 1 can be modified as appropriate, for example, by allowing only the concentration zone in front of the outer cylinder screen to rotate.

[0021] A cleaning pipe 13 is provided above the outer cylinder screen 5, and the outer cylinder nine This clears blockages in the lean 5. The cleaning pipe 13 extends along the axial direction of the screw shaft 7, and by spraying cleaning fluids such as cleaning liquid or air from multiple nozzles 14 installed at predetermined intervals toward the screen surface, sludge adhering to the outer cylinder screen 5 can be removed.

[0022] The outer cylinder screen cleaning process efficiently cleans the entire screen surface by spraying cleaning fluid while rotating the outer cylinder screen 5. During outer cylinder screen cleaning, the screw shaft 7 does not rotate; only the outer cylinder screen 5 rotates. The shape and installation method of the cleaning pipe 13 are selected as appropriate depending on the conditions.

[0023] Figure 3 is an enlarged cross-sectional view of a portion of the starting end of the screw press 1 in another embodiment 1. In this embodiment, the screw shaft 7 and the outer cylinder screen 5 are driven by a single screw drive machine (not shown). The screw shaft 7, with screw blades 6 arranged around it, is rotatably mounted inside the cylindrical outer cylinder screen 5, which is rotatably supported on the front frame 3.

[0024] A cylindrical screw shaft end plate 17 is connected to the starting end of the screw shaft 7, allowing it to rotate integrally with the screw shaft 7. A ratchet pawl 15a (left-hand diagonal) is formed protruding from the outer circumferential surface of the screw shaft end plate 17, which can be locked into a stopper 16a (right-hand diagonal), described later.

[0025] On the other hand, a cylindrical outer screen end plate 18 is connected to the starting end of the outer screen 5, extending from the starting end toward the front frame 3. By rotating the outer screen end plate 18, the outer screen 5 can be rotated as a whole.

[0026] The outer cylinder screen end plate 18 is provided with a stopper 16a, which allows the ratchet pawl 15a, which is formed to protrude from the screw shaft end plate 17, to be engaged from only one direction. The outer cylinder screen end plate 18 is configured to rotate integrally with the screw shaft end plate 17.

[0027] Furthermore, a ratchet pawl 15b (left-hand diagonal section) is formed to protrude from the outer cylinder screen end plate 18, and can be locked into a stopper 16b (right-hand diagonal section), which will be described later. The ratchet pawl 15b is configured to be locked into the stopper 16b from only one direction, thereby preventing the outer cylinder screen 5, which can rotate integrally with the outer cylinder screen end plate 18, from rotating in one direction.

[0028] A cylindrical support plate 19 is connected to the front frame 3, and a stopper 16b is installed on the support plate 19. Although the stopper 16b is installed on the front frame 3 via the support plate 19, it may also be installed directly on the front frame 3. The installation method and position of the stoppers 16a and 16b should be selected as appropriate depending on the conditions.

[0029] Figure 4 is a cross-sectional view AA of the screw press in another embodiment 1. Figure 4 shows the screw press 1 in the configuration detailed in Figure 3. The screw shaft end plate 17, which rotates integrally with the screw shaft 7 (Figure 3), rotates counterclockwise during dewatering operation and clockwise during outer cylinder screen cleaning, as viewed from the sludge supply side.

[0030] A ratchet pawl 15a is formed on the outer circumferential surface of the screw shaft end plate 17, projecting radially from the center of the screw shaft 7. The ratchet pawl 15a extends radially with a predetermined width, and is formed so that one side is straight and the other side is tapered.

[0031] The outer cylinder screen end plate 18 has a screw shaft end plate 17 passing through its center, and is configured to rotate integrally with the screw shaft 7 via the screw shaft end plate 17.

[0032] The outer cylinder screen end plate 18 is provided with a stopper 16a that, under normal conditions, protrudes toward the center of the screw shaft 7 due to the biasing force of the elastic body 20. Since the stopper 16a is installed so as to protrude within the rotational trajectory of the ratchet pawl 15a under normal conditions, it can lock the ratchet pawl 15a.

[0033] The stopper 16a extends toward the center of the screw shaft 7 with a predetermined width, and is formed so that one side is straight and the other side is tapered.

[0034] When the ratchet pawl 15a, which rotates in the forward direction during the dewatering operation, contacts the stopper 16a, the internal elastic body 20 undergoes elastic deformation due to the pressing force of the ratchet pawl 15a, causing it to swing outward (in the direction in which the elastic body 20 contracts). With this configuration, the screw shaft end plate 17, which rotates in the forward direction during the dewatering operation, can rotate continuously while pushing the stopper 16a outward, so that the rotation of the screw shaft 7, which rotates integrally with the screw shaft end plate 17, is not hindered.

[0035] On the other hand, when the screw shaft 7 is reversed during outer cylinder screen cleaning, the ratchet pawl 15a engages with the stopper 16a. With the ratchet pawl 15a engaged with the stopper 16a, the outer cylinder screen end plate 18, which receives the rotational force of the reversed screw shaft 7, also reverses. Since the outer cylinder screen end plate 18 is a component connected to the outer cylinder screen 5, the outer cylinder screen 5 rotates together with the rotation of the screw shaft 7.

[0036] A ratchet pawl 15b is formed on the outer circumferential surface of the outer cylinder screen end plate 18, projecting radially from the center of the outer cylinder screen 5. The ratchet pawl 15b extends radially with a predetermined width, and is formed so that one side is straight and the other side is tapered.

[0037] A stopper 16b is provided on the support plate 19 on the front frame 3, which under normal conditions protrudes toward the center of the screw shaft 7 due to the biasing force of the elastic body 20. The stopper 16b is installed so as to protrude within the rotational trajectory of the ratchet pawl 15b under normal conditions, thereby allowing the ratchet pawl 15b to be locked in place.

[0038] The stopper 16b extends toward the center of the screw shaft 7 with a predetermined width, and is formed so that one side is straight and the other side is tapered.

[0039] The stopper 16b engages the ratchet pawl 15b during the dewatering operation, preventing the forward rotation of the outer cylinder screen 5 connected to the outer cylinder screen end plate 18. On the other hand, when the ratchet pawl 15b, which reverses direction during outer cylinder screen cleaning, makes contact, the internal elastic body 20 undergoes elastic deformation under the pressure of the ratchet pawl 15b, causing it to oscillate outward (in the direction in which the elastic body 20 contracts). With this configuration, the outer cylinder screen end plate 18, which reverses direction during outer cylinder screen cleaning, can rotate continuously while pushing the stopper 16b outward, thus preventing the rotation of the outer cylinder screen 5 from being hindered.

[0040] In this configuration, the outer cylinder screen 5 gradually rotates due to the frictional force of the screw shaft 7 that rotates during the dewatering operation, and is fixed in a position where the ratchet pawl 15b and stopper 16b engage. Therefore, the starting position of the ratchet pawl 15b at the start of outer cylinder screen cleaning is always the same. In other words, the outer cylinder screen 5 always starts rotating from a fixed position at the start of cleaning.

[0041] The shapes of the ratchet pawls 15a, 15b and stoppers 16a, 16b are not limited to these and can be changed as appropriate according to the design conditions. Also, although the stoppers 16a, 16b are made of an elastic body 20 such as a coil spring, they are not particularly limited. The screw shaft end plate 17 can also be any configuration that includes a ratchet pawl 15a that rotates integrally with the screw shaft 7, such as a configuration in which the screw shaft 7 is extended into the front frame 3 and the ratchet pawl 15a is provided on the outer circumference of the screw shaft 7, and can be set as appropriate according to the conditions.

[0042] Figure 5 is a cross-sectional view AA of the screw press in another embodiment 2. Figure 5 shows an additional configuration of the other embodiment 1 detailed in Figure 4, with the stopper 16b added, and the other configurations are the same. In the configuration of Figure 4, since only one stopper 16b is installed at the top, the ratchet pawl 15b is always engaged with the stopper 16b during the dewatering operation, and sludge filtration and dewatering are performed. On the other hand, in the configuration of Figure 5, since four stoppers 16b are installed at predetermined intervals, sludge filtration and dewatering can be performed with the ratchet pawl 15b engaged with the desired stopper 16b during the dewatering operation.

[0043] In the configuration shown in Figure 4, the screen bottom surface 28 is always fixed in the same position during dewatering, and sludge is filtered and dewatered. As a result, filtration pressure (internal pressure and gravity) is applied locally to the screen bottom surface 28. However, in the configuration shown in Figure 5, the position of the screen bottom surface 28 can be changed as needed during dewatering, thus preventing the filtration pressure from being applied locally to the screen bottom surface 28.

[0044] In the configuration shown in Figure 5, the position of the ratchet pawl 15b during the next dewatering operation is changed by appropriately modifying the stopper 16b that engages the ratchet pawl 15b when the outer cylinder screen cleaning is completed. Consequently, the starting position of rotation of the outer cylinder screen 5 when the next outer cylinder screen cleaning begins is changed.

[0045] Figure 6 is a schematic diagram of the stopper in another embodiment 2. As shown in Figure 6(a), the stoppers 16a and 16b consist of a contact body 21 that receives a pressing force when the ratchet pawls 15a and 15b (Figure 4) come into contact with it and swings outward, an elastic body 20 that is close to the contact body 21 and normally applies a biasing force to the contact body 21, and a fixing part 22 that fixes the elastic body 20 located inside and the contact body 21 that is close to the elastic body 20 to the outer cylinder screen end plate 18 and support plate 19 (Figure 4). The contact body 21 is configured to prevent it from falling by a support part 23 provided on the fixing part 22.

[0046] Of the stoppers 16a and 16b, each of the four stoppers 16b... fixed to the support plate 19 is equipped with a detection device 26. The detection device 26 consists of a detection body 24 that receives the pressing force and a detection switch 25 that detects when the detection body 24 receives the pressing force.

[0047] Since the detection body 24 is installed on the elastic body 20 or the contact body 21, it is pushed outward along with the contact body 21 which swings outward in response to the pressing force of the ratchet pawl 15b. The detection switch 25 is formed of a contact-type sensor such as a limit switch, and can detect contact with the detection body 24. With this configuration, when contact between the detection body 24 and the detection switch 25 is detected, it can be determined that the contact body 21 has received a pressing force. The detection switch 25 may be installed on the support plate 19 or on the front frame 3, and the installation position is determined appropriately according to the design conditions.

[0048] The detection switch 25 is installed on each stopper 16b..., and is configured to detect when a pressing force is received from the ratchet pawl 15b at each stopper 16b.... The detection device 26 only needs to be a mechanism that can detect when a stopper 16b is subjected to a pressing force from the ratchet pawl 15b. For this reason, it may be configured as follows: a pressure switch system, as shown in Figure 6(b), in which a pressure switch (detection switch 25) is installed at the point of contact with the elastic body 20 to detect when pressure is received; or a proximity switch system, as shown in Figure 6(c), in which a proximity switch (detection switch 25) can detect when the detection body 24 is pushed outward without contact.

[0049] Since the detection device 26 is installed for the purpose of identifying the position of the ratchet pawl 15b during outer cylinder screen cleaning, any device capable of identifying the position, such as an imaging device (not shown), may be used. [Examples]

[0050] Figure 7 is an explanatory diagram of the cleaning method for the outer cylinder screen in this embodiment. In this embodiment, the screw shaft 7 and the outer cylinder screen 5 are each rotated by separate drive units (not shown). During outer cylinder screen cleaning, the outer cylinder screen drive unit is driven to rotate the outer cylinder screen 5 while supplying cleaning fluid. The cleaning fluid is sprayed from the nozzle 14 of the cleaning pipe 13 located above the screen toward the screen surface. At this time, since the cleaning fluid is supplied while the outer cylinder screen 5 is rotating, sludge adhering to the screen surface can be efficiently removed.

[0051] As an initial setting, the rotation angle θ of the cleaning fluid supply zone, which is calculated in advance from the screen bottom surface 28 in the direction of screen rotation, and the rotation speed of the outer cylinder screen 5 during outer cylinder screen cleaning are set. The cleaning fluid supply zone is the section in which the cleaning fluid is sprayed onto the screen surface, and as the outer cylinder screen 5 passes through this zone, the cleaning fluid removes sludge adhering to the screen surface.

[0052] At the start of the cleaning process, the screen drive is activated, and when the outer cylinder screen 5 begins to rotate, the rotation angle θ of the screen bottom surface 28 is measured. While the screen bottom surface 28 is rotating at θ / 360 degrees, the rotation speed of the outer cylinder screen 5 is reduced to extend the time that cleaning fluid is supplied to the screen surface, thereby intensively cleaning the screen bottom surface 28. The screen bottom surface 28 is fixed as the filtration bottom surface during the preceding dewatering operation, and sludge is filtered and dewatered while under filtration pressure, causing localized clogging. Therefore, when the screen bottom surface 28 passes through the cleaning fluid supply zone during the outer cylinder screen cleaning process, the cleaning intensity is increased and the screen bottom surface 28 is intensively cleaned, thereby eliminating clogging of the screen bottom surface 28.

[0053] This ensures that clogging across the entire screen surface is eliminated without uneven cleaning, thus preventing a decrease in dewatering efficiency during the next dewatering operation. Furthermore, by increasing the cleaning intensity only while the screen bottom surface 28 passes through the cleaning fluid supply zone, the screen bottom surface 28 is cleaned intensively, allowing for efficient elimination of clogging across the entire screen surface without reducing the overall operating efficiency of the equipment.

[0054] In this embodiment, the rotation angle θ is measured after the outer cylinder screen 5 starts to rotate, but the method for determining when the screen bottom surface 28 has rotated to the position of the cleaning fluid supply zone is to calculate it by time, or position This is performed by calculation using the detection means 31A. The time-based calculation method involves pre-determining the time interval during which the screen bottom surface 28 rotates θ / 360 within the cleaning fluid supply zone. When the corresponding time interval is detected by a timer or the like, it is determined that the screen bottom surface 28 is passing through the cleaning fluid supply zone, and the cleaning intensity is increased. The width of the screen bottom surface 28 is set in advance to a predetermined width in the direction of rotation.

[0055] positionThe calculation method by the detection means 31A involves irradiating light onto a detection unit 29 installed on the outer cylindrical screen 5 and detecting the reflection of the irradiated light. The detection unit 29 is installed across the width direction of the screen bottom surface 28, which is set to a predetermined width in the rotational direction. In addition, a non-contact sensor 30A that irradiates light toward the starting point of the cleaning fluid supply zone and a non-contact sensor 30B that irradiates light toward the ending point of the cleaning fluid supply zone are installed, and light is irradiated from each non-contact sensor 30 toward the detection unit 29.

[0056] Since the detection unit 29 is formed from a reflector and each non-contact sensor 30 is an optical sensor, when the screen bottom surface 28 rotates, when the starting end of the detection unit 29 passes the starting point of the cleaning fluid supply zone, the light emitted from the non-contact sensor 30A is reflected by the detection unit 29, and the reflected light is received by the non-contact sensor 30A. At this time, it can be determined that the screen bottom surface 28 has started to pass through the cleaning fluid supply zone. Subsequently, when the light emitted from the non-contact sensor 30B is reflected from the detection unit 29, it can be determined that the screen bottom surface 28 has finished passing through the cleaning fluid supply zone.

[0057] When the non-contact sensor 30A detects reflected light, the screen bottom surface 28 begins to pass through the cleaning fluid supply zone, and when the non-contact sensor 30B detects reflected light, it is determined that the screen bottom surface 28 has finished passing through the cleaning fluid supply zone. Therefore, the cleaning intensity is increased when the non-contact sensor 30A detects reflected light and returned to its original intensity when the non-contact sensor 30B detects reflected light.

[0058] The configuration of the detection unit 29 and the non-contact sensor 30 is not limited to this. For example, as shown in Figure 8, the detection unit 29 may be installed at the lowest point of the outer cylinder screen 5, and the non-contact sensor 30 may be installed at a position that takes into account the predetermined width of the screen bottom surface 28, thereby detecting when the screen bottom surface 28 has passed through the cleaning fluid supply zone. Alternatively, the detection unit 29 may be partially installed on the outer cylinder screen bottom surface 28.

[0059] Figure 9 is an explanatory diagram of the cleaning method for the outer cylinder screen in another embodiment 1. In another embodiment 1, the screw shaft 7 is reversed by a screw drive (not shown), and the outer cylinder screen 5 is cleaned while the ratchet pawl 15a is engaged with the stopper 16a and the outer cylinder screen 5 is rotated together. The concentrated cleaning method for the screen bottom surface 28 is the same as in the embodiment in Figure 7, after calculating the rotation angle θ, the screen bottom surface 28 is positioned in the cleaning fluid supply zone for a certain amount of time. position The rotation angle θ is calculated by means such as the detection means 31A. The method for calculating the rotation angle θ and the method for calculating when the screen bottom surface 28 passes through the cleaning fluid supply zone are the same as in Figure 7 and are therefore omitted. However, in this configuration, there is a loss of time when the outer cylinder screen 5 starts to rotate, so the rotation angle θ is determined by measuring the rotation of the outer cylinder screen 5 while taking this into consideration.

[0060] Loss time is the time from the start of rotation of the outer cylinder screen 5 until the ratchet pawl 15a engages with the stopper 16b. In the configuration shown in Figure 7, the outer cylinder screen 5 is driven by a screen drive unit separate from the screw drive unit, so the outer cylinder screen 5 starts rotating immediately after the drive unit is activated. On the other hand, in this configuration, the outer cylinder screen 5 starts rotating after the screw drive unit is activated and the ratchet pawl 15a engages with the stopper 16a. In other words, the outer cylinder screen 5 does not start rotating immediately after the screw drive unit is activated, so the screw - Axis The time between the start of rotation of part 7 and the start of rotation of the outer cylinder screen 5 is considered lost time. Therefore, in this configuration, the moment when the ratchet pawl 15a engages with the stopper 16a is detected, and it is determined that the outer cylinder screen 5 will start to rotate at that point, and the measurement of the rotation angle θ is started.

[0061] The detection method is attached to the stopper 16a Locking This is done using the detection means 31B. LockingThe detection means 31B is a pressure-sensitive switch, such as a tape switch, capable of detecting pressing force, and is installed on the locking surface with the ratchet pawl 15a. This allows detection that when the screw shaft 7 is rotated at the start of outer cylinder screen cleaning, the ratchet pawl 15a engages with the stopper 16a and pressing force is applied. When the pressing force is detected, it can be determined that the outer cylinder screen 5 will start rotating.

[0062] As shown in the diagram, pressure-sensitive switch ( Locking The detection means 31B) may be installed on the stopper 16b side. In this case, Locking The detection means 31B is installed on the locking surface of the stopper 16b, and the ratchet pawl 15b, which was locked to the stopper 16b during the preceding dewatering operation, separates from the stopper 16b, that is, Locking When it is detected that no pressing force is being applied to the detection means 31B, it can be determined that the outer cylinder screen 5 has started to rotate.

[0063] Locking The detection means 31B is installed at least one location on the stoppers 16a and 16b, but the installation location may be changed as appropriate depending on the conditions, such as installing it on the ratchet pawl 15a and 15b side.

[0064] In Figures 7 and 9, the rotation angle θ was calculated using time and a non-contact sensor 30, but a contact sensor (not shown) may be provided to directly detect contact with the detection unit 29 (Figure 7). The installation position, material, number, and sensor type of the detection unit 29 are not limited to these. An imaging device may be installed to continuously image the bottom surface 28 of the screen to detect passage over the bottom surface 28, or a combination of two or more methods may be used.

[0065] Furthermore, while the cleaning intensity is increased by reducing the rotation speed of the outer cylinder screen 5, it is sufficient to concentrate cleaning on the screen bottom surface 28. Therefore, any method that can increase the cleaning intensity is acceptable, such as increasing the cleaning pressure of the cleaning fluid, increasing the amount of cleaning water, using cleaning liquid and cleaning air together as the cleaning fluid, or spraying hot water or chemical solution, only while the screen bottom surface 28 is passing through the cleaning fluid supply zone. Two or more methods may also be combined, such as reducing the rotation speed of the outer cylinder screen 5 and increasing the cleaning pressure of the cleaning fluid.

[0066] Furthermore, while the cleaning of the outer cylinder screen is currently concentrated only on the screen bottom surface 28, the entire screen may be monitored using an imaging device, and if clogging occurs in areas other than the screen bottom surface 28, those areas may also be cleaned intensively.

[0067] Figures 10 to 12 are explanatory diagrams of the cleaning method for the outer cylinder screen in another embodiment 2. This configuration is an arrangement in which multiple stoppers 16b are installed, as shown in the other embodiment 1 in Figure 9, with a detection device 26 positioned outside each stopper 16b. Four stoppers 16b are installed at 90-degree intervals. Of the four stoppers 16b, the stopper 16b located vertically above the center of the screw shaft 7 is defined as stopper 16b1, and the stoppers installed clockwise at 90-degree intervals from stopper 16b1 are defined as 16b2, 16b3, and 16b4.

[0068] Furthermore, the screen bottom surface 28 has a predetermined width set in the direction of rotation, and the position on the screen bottom surface 28 side when the ratchet pawl 15b engages with the stopper 16b1 is defined as "A", the position on the screen bottom surface 28 side when it engages with the stopper 16b2 is defined as "B", the position on the screen bottom surface 28 side when it engages with the stopper 16b3 is defined as "C", and the position on the screen bottom surface 28 side when it engages with the stopper 16b4 is defined as "D".

[0069] Furthermore, the section where the cleaning pipe 13 is located and the cleaning fluid is sprayed onto the screen surface (between stoppers 16b1 and 16b4) is defined as the cleaning fluid supply zone, and the sections where cleaning fluid is not supplied are defined as non-cleaning fluid supply zone 1 (between stoppers 16b1 and 16b2), non-cleaning fluid supply zone 2 (between stoppers 16b2 and 16b3), and non-cleaning fluid supply zone 3 (between stoppers 16b3 and 16b4).

[0070] The following details the specific cleaning method. After the dewatering operation is completed, the outer cylinder screen 5 is reversed at a predetermined speed, and the rotation speed is temporarily reduced to increase the cleaning intensity as the bottom surface 28 of the outer cylinder screen passes through the cleaning fluid supply zone. For example, if solid-liquid separation of sludge is performed with position "A" fixed on the screen bottom surface 28 side during the preceding dewatering operation, the filtration pressure is concentrated on the screen bottom surface 28 "A", and it is determined that local clogging has occurred, so the cleaning intensity is increased when the screen bottom surface 28 "A" begins to pass through the cleaning fluid supply zone. By intensively cleaning the screen bottom surface 28 "A", it is possible to reliably remove solid matter adhering to the screen bottom surface 28.

[0071] Then, after the screen bottom surface 28 "A" has passed through the cleaning fluid supply zone, the rotation speed is returned to a predetermined speed. Subsequently, when the outer cylinder screen bottom surface 28 "A" passes through the cleaning fluid supply zone again, the rotation speed is reduced again. By repeating this operation, localized clogging of the screen bottom surface 28 "A" can be eliminated, and the entire screen surface is uniformly cleaned.

[0072] Figure 11 shows the state in which the screen bottom surface "A" in Figure 10 starts passing through the cleaning fluid supply zone from a position rotated 90 degrees clockwise. However, since the rotation angle θ from the screen bottom surface 28 to the cleaning fluid supply zone and the angle θ between each stopper 16b are configured to be the same angle, when the screen bottom surface 28 "A" starts passing through the cleaning fluid supply zone, the ratchet pawl 15b starts passing through the non-cleaning fluid supply zone 2. Therefore, when the detection device 26B detects that the ratchet pawl 15b has applied pressure to the stopper 16b2, it determines that the screen bottom surface 28 "A" has started passing through the cleaning fluid supply zone, and the rotation speed is reduced to concentrate cleaning on the screen bottom surface 28 "A".

[0073] Subsequently, as shown in Figure 12, when the screen bottom surface "A" rotates 90 degrees clockwise from the position in Figure 11 and begins to pass through the non-cleaning fluid supply zone 1, the ratchet pawl 15b rotates to the position of the stopper 16b3. When the detection device 26C detects that a pressing force has been applied to the stopper 16b3, it is determined that the screen bottom surface 28 "A" has begun to pass through the non-cleaning fluid supply zone 1, and the rotation speed of the outer cylinder screen 5 is returned to a predetermined speed.

[0074] In this configuration, the position of the screen bottom surface 28 during the dewatering operation can be appropriately changed to prevent localized application of filtration pressure to the screen bottom surface 28, and the screen bottom surface 28 can be intensively cleaned during outer cylinder screen cleaning, thereby efficiently eliminating clogging of the screen bottom surface 28.

[0075] In another embodiment 2, as shown in Figure 10, each stopper 16b is provided with a detection body 24... and a detection switch 25... is provided outside of it, and the detection switches 25... are installed at 90-degree intervals, similar to the stoppers 16b... 5...is used to determine that a pressing force has been applied when it is detected that each detection element 24... has come into contact with each detection switch 25.... Also, as the screen bottom surface 28 passes through the cleaning fluid supply zone, the screen bottom surface 28 rotates while facing the spray nozzle 14, so that any attached solid matter is efficiently removed by the supplied cleaning fluid. In this configuration, four stoppers 16b are arranged at 90-degree intervals, but it is sufficient to install at least two or more, and the installation interval is not limited. The installation position and number of each detection device 26 may also be changed as appropriate.

[0076] Furthermore, the screen bottom surface 28 may have its rotation speed reduced each time it passes through the cleaning fluid supply zone during cleaning to increase the cleaning intensity. However, it is also possible to modify the method as appropriate, such as increasing the cleaning intensity only once during the multiple rotations of the outer cylinder screen 5, or increasing the cleaning intensity only once every two rotations. The method for increasing the cleaning intensity may also involve changing the supply method, such as temporarily increasing the amount of cleaning fluid supplied.

[0077] The position and number of cleaning pipes 13 are not limited, and they may be installed not only between stoppers 16b1 and 16b4, but also between stoppers 16b1 and 16b2, allowing cleaning fluid to be sprayed from multiple locations. In this case, the opportunities for concentrated cleaning increase, making it possible to remove sludge in a short time, even if the screen bottom surface 28 is severely clogged.

[0078] The method for calculating when the screen bottom surface 28 has passed the cleaning fluid supply zone is set appropriately according to conditions such as time and non-contact sensor 30, as in Figures 7 and 9. However, in this configuration, as in Figure 9, the ratchet pawl 15a is engaged with the stopper 16a to rotate the outer cylinder screen 5, so at the start of rotation of the outer cylinder screen 5 Locking After detecting that the ratchet pawl 15a has engaged with the stopper 16a using the detection means 31B, the measurement of the rotation angle θ is started.

[0079] The present invention is not limited to the embodiments described in detail above. Modifications can be made as appropriate without departing from the spirit of the invention. [Industrial applicability]

[0080] The screw press outer cylinder screen cleaning method of the present invention allows for concentrated cleaning of specific areas of the outer cylinder screen during cleaning, thus maintaining processing efficiency even when handling raw materials with properties that are prone to screen clogging. Because it can handle various raw materials with different properties, it can be applied to a wide range of fields. [Explanation of symbols]

[0081] 1 Screw press 5. Outer cylinder screen 7 Screw shaft 13. Washing pipe 15a, 15b Ratchet pawl 16a, 16b Stopper 28 Screen bottom 29 Detection unit 30 Non-contact sensors 31A position Detection means 31B Locking Detection means

Claims

1. In a screw press having a cleaning pipe (13) extending along the axial direction of the screw shaft (7) and an outer cylindrical screen (5) that rotates and passes through a cleaning fluid supply zone into which cleaning fluid is supplied toward the screen surface, The rotation angle θ of the cleaning fluid supply zone, which was calculated in advance from the bottom surface (28) of the screen in the direction of screen rotation, The rotation speed of the outer cylinder screen (5) during outer cylinder screen cleaning is set. The rotation angle θ of the screen bottom surface (28) is measured from the start of rotation of the outer cylindrical screen (5). The screen bottom surface (28) rotates at θ / 360 degrees, increasing the cleaning intensity only while passing through the cleaning fluid supply zone. A method for cleaning the outer cylinder screen of a screw press, characterized by the following features.

2. The measurement of the rotation angle θ is: This is calculated based on the elapsed time since the start of rotation of the outer cylindrical screen (5), or based on the detection result of the position detection means (31A). The method for cleaning the outer cylinder screen of a screw press according to feature 1.

3. The cleaning strength is determined by changing at least one of the following: the rotation speed of the outer cylinder screen (5) or the method of supplying the cleaning fluid. The method for cleaning the outer cylinder screen of a screw press according to feature 1.

4. The position detection means (31A) is The system includes at least one of the following: a non-contact sensor (30) that illuminates a detection unit (29) installed on the bottom surface (28) of the screen; a contact sensor that detects contact with the detection unit (29); and an imaging device that photographs the bottom surface (28) of the screen. The method for cleaning the outer cylinder screen of a screw press according to feature 2.

5. The device comprises a ratchet pawl (15a) that rotates integrally with the screw shaft (7), a stopper (16a) located on the rotational path of the ratchet pawl (15a) and engaging with the ratchet pawl (15a) to rotate the outer cylinder screen (5), a ratchet pawl (15b) that rotates integrally with the outer cylinder screen (5), and a stopper (16b) located on the rotational path of the ratchet pawl (15b) and engaging with the ratchet pawl (15b) to obstruct the rotation of the outer cylinder screen (5), When the ratchet pawl (15a) is engaged with the stopper (16a) at the start of cleaning the outer cylinder screen (5), the locking detection means (31B) detects that the ratchet pawl (15a) has engaged with the stopper (16a), It is determined that the outer cylinder screen (5) has started to rotate. A method for cleaning the outer cylinder screen of a screw press according to any one of claims 1 to 4.

6. The lock detection means (31B) is A pressure-sensitive switch is installed at one or more locations between the locking surfaces of the ratchet pawl (15a) and the stopper (16a), or between the locking surfaces of the ratchet pawl (15b) and the stopper (16b). The method for cleaning the outer cylinder screen of a screw press according to feature 5.

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