Clogging preventive mechanism in screw press, and clogging preventive method using the same

Abstract

To provide a clogging preventive mechanism in a screw press, and a clogging preventive method using the same, that can prevent generation of local clogging by sequentially changing a position of a screen bottom surface during dehydration operation.SOLUTION: A screw press 1 is provided with a screw shaft 7 having a screw blade 6 circumferentially disposed in an outer cylindrical screen 5 that is freely rotatable. The screw press includes: a screw shaft end plate 17 which rotates integrally with the screw shaft 7, and has a ratchet pawl 15a projecting in a radial direction from the shaft center; an outer cylindrical screen end plate 18 which is provided with a stopper 16a positioned in a rotary zone of the ratchet pawl 15a, and has a ratchet pawl 15b projecting in a radial direction from the shaft center; a plurality of stoppers 16b positioned in a rotary zone of the ratchet pawl 15b; and a detection device 26 for detecting that each stopper 16b has received pressing force of the ratchet pawl 15b and oscillated outward. Thereby, since a position of a screw bottom surface can be changed, local clogging does not occur in the screw press.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a technique for preventing clogging of an outer cylinder screen, and particularly to a clogging prevention mechanism in a screw press and a clogging prevention method using the same, in which local clogging does not occur during dehydration operation by changing the position of the bottom surface of the screen after screen cleaning.

Background Art

[0002] Conventionally, screw presses for concentrating and dehydrating organic sludge such as sewage, night soil, or food production and processing wastewater have been generally known. For example, Patent Document 1 discloses a screw press in which a screw shaft with spiral blades wound around a cylindrical outer cylinder screen having a large number of micropores is rotatably installed, and the stock solution supplied to one end of the screw shaft is filtered and dehydrated while being conveyed toward the other end. The screw press disclosed in Patent Document 1 is a technique for rotating the screw shaft and the screen using one drive device. During the dehydration operation, only the screw shaft rotates counterclockwise, and the screen rotates together with the screw shaft that rotates clockwise during screen cleaning.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, the filtration and dewatering of a screw press are performed over the entire surface of the screen. As the filtration pressure, in addition to the internal pressure, gravity is generated. In particular, the bottom surface of the screen that is subject to the internal pressure and gravity has the problem that clogging of the filtration surface tends to progress. As shown in FIG. 3, the screw press of Patent Document 1 is configured such that the screen stops with the ratchet pawls provided on the end plate on the other end side of the screen engaged with the stoppers provided on the screen end plate. Since the stoppers for engaging the ratchet pawls are provided only at one location, the position of the filtration bottom surface at the time of screen stop is the same location every time. Since the dewatering operation is repeated in this state, clogging has occurred locally on the bottom surface of the screen.

[0005] The present invention provides a clogging prevention mechanism in a screw press and a clogging prevention method using the same, which can prevent local clogging from occurring during the dewatering operation by providing ratchet pawls on the outer cylinder screen end plate connected to the outer cylinder screen and installing a plurality of stoppers for locking the ratchet pawls so that the position of the filtration bottom surface at the time of screen stop can be appropriately changed.

Means for Solving the Problems

[0006] The present invention provides a screw press which internally provides a screw shaft with screw blades wound around a rotatably supported outer cylinder screen, filters and dehydrates a stock solution supplied to the starting end side while conveying it toward the terminal end side by rotation of the screw shaft, and removes sludge adhering to the outer cylinder screen by injecting a cleaning fluid from a cleaning pipe onto the screen surface. The screw press includes a ratchet claw that rotates integrally with the screw shaft and protrudes radially from the center of the screw shaft, and a stopper that is located in the rotation orbit of the ratchet claw, swings outward by the pressing force of the ratchet claw during the dehydration operation, and locks the ratchet claw to rotate the outer cylinder screen integrally with the screw shaft during the cleaning of the outer cylinder screen; a ratchet claw that rotates integrally with the outer cylinder screen and protrudes radially from the center of the outer cylinder screen, and a plurality of stoppers that are located in the rotation orbit of the ratchet claw, lock the ratchet claw to inhibit the rotation of the outer cylinder screen during the dehydration operation, and swing outward by the pressing force of the ratchet claw during the cleaning of the outer cylinder screen; and a detection device that detects that the stopper has swung outward under the pressing force of the ratchet claw. By having these components, the position of the bottom surface of the outer cylinder screen can be appropriately changed at the end of the cleaning of the outer cylinder screen.

[0007] The screw shaft has a screw shaft end plate connected to the starting end portion, and rotates the ratchet claw protruding from the screw shaft end plate integrally, so that the ratchet claw of the screw shaft end plate can rotate during the dehydration operation.

[0008] The outer cylinder screen has an outer cylinder screen end plate connected to the end portion, and rotates the ratchet claw protruding from the outer cylinder screen end plate integrally with the ratchet claw locked to the stopper provided on the outer cylinder screen end plate, so that the ratchet claw of the outer cylinder screen end plate can rotate during the cleaning of the outer cylinder screen.

[0009] The detection device is provided on each stopper, and includes a detection body that is pushed upward outward under the pressing force during the cleaning of the outer cylinder screen and a contact or non-contact detection switch that detects the detection body, so that the position of the ratchet claw during the cleaning of the outer cylinder screen can be grasped.

[0010] Using the clogging prevention mechanism in the screw press, when cleaning the outer cylinder screen, a detection device detects that each stopper has received the pressing force of the ratchet claw. When it is detected that a predetermined stopper has received the pressing force, the rotation of the screw shaft is stopped. During the dehydration operation, the ratchet claw is locked to a desired stopper, and the position of the bottom surface of the screen of the outer cylinder screen can be changed, so that local clogging does not occur in the outer cylinder screen during the dehydration operation, and thus the filtration operation can be stably performed.

Effect of the Invention

[0011] The present invention is configured such that the outer cylinder screen can be rotated by using a drive mechanism of a screw shaft. Since the screw shaft and the outer cylinder screen can be driven by one drive source, operation with low power is possible. During the dehydration operation, filtration dehydration is performed with the position of the bottom surface of the screen of the outer cylinder screen changed, so that the filtration pressure is not concentrated on a predetermined portion of the screen. Accordingly, local clogging does not occur in the screen, so that a decrease in dehydration efficiency can be prevented. Since the cleaning frequency of the outer cylinder screen can also be reduced, it is possible to reduce the cleaning time and the amount of cleaning water, and energy saving can also be achieved. In addition, since it is only necessary to add a stopper or the like to the mechanism of the conventional screw press, it can be applied to an existing apparatus without significantly changing the design.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 is a longitudinal side view of a screw press according to the present invention. The screw press 1 has an outer cylinder screen 5 having a filtering surface on its circumference bridged between a front frame 3 and a rear frame 4 erected on a stand 2, and a screw shaft 7 around which screw blades 6 are wound is provided inside. The screw shaft 7 disposed inside the outer cylinder screen 5 increases in diameter in a tapered shape from the start end side to the end end side, and the distance between the outer cylinder screen 5 and the screw shaft 7 is relatively decreased in the extending direction. 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 at the start end side of the outer cylinder screen 5.

[0014] A screw drive shaft 10 is connected to the rear end portion of the screw shaft 7, and a drive sprocket 11 is fitted to the screw drive shaft 10. This sprocket 11 is driven by a screw drive machine (not shown) to rotate the screw shaft 7. In the present embodiment, the screw shaft 7 is driven by a single screw drive machine, and the screw shaft 7 is rotated forward during dehydration and reversed during cleaning of the outer cylinder screen.

[0015] The sludge supplied from the supply hole 9 flows into a filtration chamber 12 formed between the outer cylinder screen 5 and the screw shaft 7, and then is filtered and dehydrated while being conveyed from the start end side to the end end side by the screw blades 6. The conveyed sludge forms a cake while separating the filtrate from the outer cylinder screen 5 and is discharged from the end end side as a dehydrated cake.

[0016] A cleaning pipe 13 is arranged above the outer cylinder screen 5 to eliminate the clogging of the outer cylinder screen 5. The cleaning pipe 13 is provided along the axial direction of the outer cylinder screen 5, and by injecting a cleaning fluid such as a cleaning liquid or air from a plurality of cleaning nozzles 14 installed at a predetermined interval, the sludge adhering to the outer cylinder screen 5 can be removed.

[0017] In this embodiment, the cleaning pipe 13 extends from the sludge supply side to the discharge side of the outer cylinder screen 5, and by injecting the cleaning liquid while rotating the outer cylinder screen 5, the entire surface of the screen can be cleaned. However, the form and installation position of the cleaning pipe are appropriately selected according to the conditions.

[0018] Figure 2 is an enlarged side sectional view of a part of the start end side of the screw press. Inside a cylindrical outer cylinder screen 5 rotatably supported by a front frame 3, a screw shaft 7 surrounded by screw blades 6 is rotatably arranged.

[0019] At the starting end of the screw shaft 7, a screw shaft end plate 17 formed in a cylindrical shape is connected, and it is configured to be rotatable integrally with the screw shaft 7. On the outer peripheral surface of the screw shaft end plate 17, a ratchet claw 15a (left hatched part) is protrudingly formed and can be locked to a stopper 16a (right hatched part) described later.

[0020] On the other hand, at the starting end of the outer cylinder screen 5, a cylindrical outer cylinder screen end plate 18 extending from the starting end toward the front frame 3 side is connected, and by rotating the outer cylinder screen end plate 18, the outer cylinder screen 5 can be integrally rotated.

[0021] A stopper 16a is provided on the outer cylinder screen end plate 18, and the ratchet claw 15a protrudingly formed on the screw shaft end plate 17 can be locked only from one direction. Thereby, the rotation of the screw shaft 7 that can rotate integrally with the screw shaft end plate 17 in one direction can be inhibited.

[0022] In addition, a ratchet claw 15b (left hatched portion) is formed to protrude from the outer cylinder screen end plate 18 and can be locked to a stopper 16b (right hatched portion) described later. The ratchet claw 15b is configured to be lockable to the stopper 16b only from one direction, and can inhibit the rotation of the outer cylinder screen 5 that is rotatable integrally with the outer cylinder screen end plate 18 in one direction.

[0023] A cylindrical support plate 19 is connected to the front frame 3, and a stopper 16b is installed on the support plate 19. In this embodiment, the stopper 16b is installed on the front frame 3 via the support plate 19, but it may be directly installed on the front frame 3. The installation method, installation position, etc. of the stoppers 16a and 16b are appropriately selected according to conditions.

[0024] Figure 3 is a cross-sectional view taken along the line A-A of the screw press. The screw shaft end plate 17 is configured to be rotatable integrally with the screw shaft 7 (Figure 2). When viewed from the sludge supply side, it rotates counterclockwise (forward rotation) during the dehydration operation and rotates clockwise (reverse rotation) during the outer cylinder screen cleaning.

[0025] On the outer peripheral surface of the screw shaft end plate 17, a ratchet claw 15a that protrudes radially from the center of the screw shaft 7 is formed. The ratchet claw 15a has a predetermined width and extends radially, and is formed such that one side is linear and the other side is tapered.

[0026] The outer cylinder screen end plate 18 has a screw shaft end plate 17 passing through its center, and is configured to be rotatable integrally with the screw shaft 7 via the screw shaft end plate 17.

[0027] A stopper 16a that protrudes toward the center of the screw shaft 7 by the biasing force of the elastic body 20 is provided on the outer cylinder screen end plate 18 in a normal state. Since the stopper 16a is installed so as to protrude into the rotation orbit of the ratchet claw 15a in a normal state, the ratchet claw 15a can be locked.

[0028] The stopper 16a has a predetermined width and extends toward the center of the screw shaft 7, and is formed such that one side is linear and the other side is tapered.

[0029] When the ratchet pawl 15a that rotates forward during the dehydration operation contacts the stopper 16a, the internal elastic body 20 elastically deforms under the pressing force of the ratchet pawl 15a and swings outward (in the direction in which the elastic body 20 contracts). With such a configuration, the screw shaft end plate 17 that rotates forward during the dehydration operation can continuously rotate while pushing the stopper 16a upward, so the rotation of the screw shaft 7 that rotates integrally with the screw shaft end plate 17 is not inhibited.

[0030] On the other hand, when the screw shaft 7 is reversed during the outer cylinder screen cleaning, the ratchet pawl 15a locks to the stopper 16a. And in the state where the ratchet pawl 15a is locked to the stopper 16a, the outer cylinder screen end plate 18 that receives the rotational force of the reversing screw shaft 7 reverses. Since the outer cylinder screen end plate 18 is a member connected to the outer cylinder screen 5, the outer cylinder screen 5 will rotate together with the rotation of the screw shaft 7.

[0031] On the outer peripheral surface of the outer cylinder screen end plate 18, a ratchet pawl 15b that protrudes radially from the center of the outer cylinder screen 5 is formed. The ratchet pawl 15b has a predetermined width and extends radially, and is formed such that one side is linear and the other side is tapered.

[0032] On the support plate 19 provided on the front frame 3, a stopper 16b that protrudes toward the center of the screw shaft 7 by the biasing force of the elastic body 20 in the normal state is provided. Since the stopper 16b is installed so as to protrude into the rotation orbit of the ratchet pawl 15b in the normal state, the ratchet pawl 15b can be locked.

[0033] The stopper 16b has a predetermined width and extends toward the center of the screw shaft 7, and is formed such that one side is linear and the other side is tapered.

[0034] During the dehydration operation, the stopper 16b locks the ratchet pawl 15b to inhibit 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 that rotates in the reverse direction during the cleaning of the outer cylinder screen comes into contact, the internal elastic body 20 is elastically deformed under the pressing force of the ratchet pawl 15b and swings outward (in the direction in which the elastic body 20 contracts). With such a configuration, the outer cylinder screen end plate 18 that rotates in the reverse direction during the cleaning of the outer cylinder screen can continuously rotate while pushing up the stopper 16b outward, so the rotation of the outer cylinder screen 5 is not inhibited.

[0035] In this embodiment, four stoppers 16b are installed in the circumferential direction at a predetermined interval on the support plate 19. Therefore, as will be described later, the stopper 16b that locks the ratchet pawl 15b can be sequentially changed each time the cleaning of the outer cylinder screen is completed.

[0036] Note that the shapes of the ratchet pawls 15a and 15b and the stoppers 16a and 16b are not limited to this embodiment and can be appropriately changed according to the design conditions. Also, although the stoppers 16a and 16b are constituted by an elastic body 20 such as a coil spring, it is not particularly limited. Regarding the screw shaft end plate 17, as long as it has a configuration in which the ratchet pawl 15a that rotates integrally with the screw shaft 7 is provided, such as extending the screw shaft 7 into the front frame 3 and providing the ratchet pawl 15a on the outer periphery of the screw shaft 7, it is not limited.

[0037] Figure 4 is a schematic diagram of the stopper. In the present embodiment, as shown in Fig. 4(a), the stoppers 16a and 16b include a contact body 21 that swings outward under a pressing force when the ratchet claws 15a and 15b (Fig. 3) come into contact, an elastic body 20 that is close to the contact body 21 and applies a biasing force to the contact body 21 in a normal state, and a fixing portion 22 that fixes the elastic body 20 provided inside and the contact body 21 close to the elastic body 20 to the outer cylinder screen end plate 18 and the support plate 19 (Fig. 3). The contact body 21 is configured to prevent falling by a support portion 23 provided in the fixing portion 22.

[0038] Among the stoppers 16a and 16b, a detection device 26 is provided for each of the four stoppers 16b... fixed to the support plate 19. The detection device 26 includes a detection body 24 that receives a pressing force and a detection switch 25 that detects that the detection body 24 has received a pressing force.

[0039] Since the detection body 24 is installed on the elastic body 20 or the contact body 21, it is pushed upward outward along with the contact body 21 that swings outward under the pressing force of the ratchet claw 15b. Since the detection switch 25 is formed of a contact type sensor such as a limit switch, it can detect the contact of the detection body 24. With such a configuration, when the contact of the detection body 24 with the detection switch 25 is detected, it can be determined that the contact body 21 has received a pressing force. Note that the detection switch 25 may be provided on the support plate 19 or on the front frame 3, and the installation position is appropriately determined according to the design conditions.

[0040] The detection switch 25 is installed on each stopper 16b..., and is configured to be able to detect that each of all the stoppers 16b... has received a pressing force from the ratchet claw 15b. Since the detection device 26 only needs to be a mechanism that can detect that the stopper 16b has received the pressing force of the ratchet claw 15b, as shown in Fig. 4(b), a pressure switch (detection switch 25) may be provided at a position in contact with the elastic body 20 to detect that pressure has been received, or as shown in Fig. 4(c), a proximity switch method in which a proximity switch (detection switch 25) can non - contact detect that the detection body 24 has been pushed upward outward, etc. may be used to configure it.

[0041] Since the detection device 26 is installed for the purpose of identifying the position of the ratchet pawl 15b during the cleaning of the outer cylinder screen, an image detection device (not shown) or the like may be provided as a mechanism for monitoring the position of the ratchet pawl 16b that rotates during the cleaning of the outer cylinder screen, but it is not specified in this embodiment.

Example

[0042] Figure 5 is an explanatory diagram of a method for preventing clogging of the outer cylinder screen. In this embodiment, four stoppers 16b... are installed at 90-degree intervals. Among the four stoppers 16b..., the stopper 16b provided vertically upward from the center of the screw shaft 7 is defined as the stopper 16b1, and the stoppers installed at intervals of 90 degrees clockwise from the stopper 16b1 are defined as 16b2, 16b3, and 16b4.

[0043] In order to eliminate the clogging of the outer cylinder screen 5, after the dehydration operation is completed, the screw shaft 7 is reversed, and the cleaning liquid is sprayed from the cleaning pipe 13 (Figure 1) provided above the outer cylinder screen 5 toward the screen surface. While rotating the outer cylinder screen 5 below the cleaning pipe 13 for cleaning, the entire screen surface can be cleaned, and the sludge attached to the outer cylinder screen 5 can be removed.

[0044] At this time, if the stopper 16b is installed at only one location, when the screw shaft 7 is stopped after cleaning the outer cylinder screen, the ratchet pawl 15b is locked at the same location every time. Therefore, the position of the screen bottom surface 28 also stops at the same location every time.

[0045] Specifically, for example, if only the stopper 16b1 is provided above the support plate 19, when the screw shaft 7 is rotated to start the dehydration operation, the stopper 16a and the outer cylinder screen end plate 18 receive the rotational force acting in the rotational direction of the ratchet pawl 15a and the frictional force acting in the direction opposite to the rotational direction, and the outer cylinder screen 5 gradually rotates in the forward rotation direction. Then, the ratchet pawl 15b protruding from the outer cylinder screen end plate 18 is locked to the stopper 16b1.

[0046] Thus, when only one stopper 16b is provided, the ratchet pawl 15b engages with the stopper 16b at the same position every time at the end of the outer cylinder screen cleaning. Accordingly, the position of the screen bottom surface 28 is fixed. When the dehydration operation is repeatedly performed in this state, since the filtration pressure (internal pressure and gravity) acts intensively on the screen bottom surface 28, local clogging occurs in the outer cylinder screen 5.

[0047] However, in the present embodiment, four stoppers 16b are provided at predetermined intervals, and since the stopper 16b that locks the ratchet pawl 15b can be sequentially changed at the end of the cleaning of the outer cylinder screen 5, the position of the screen bottom surface 28 can be appropriately changed. After changing the position of the screen bottom surface 28, by starting the next dehydration operation, the filtration pressure does not concentrate on a specific portion of the screen. Therefore, local clogging does not occur either, and the filtration process can be stably performed. Hereinafter, a specific method for changing the position of the screen bottom surface 28 will be described in detail.

[0048] In advance, determine the stopper 16b that locks the ratchet pawl 15b at the end of the outer cylinder screen cleaning from among the four stoppers 16b.... Then, after performing the cleaning for a predetermined time, stop the rotation of the screw shaft 7 when it is detected that the predetermined stopper 16b has received the pressing force of the ratchet pawl 15b. The pressing force of the ratchet pawl 15b is detected by the detection devices 26A to 26D provided on each stopper 16b....

[0049] For example, when locking the ratchet pawl 15b to the stopper 16b1 at the end of the first outer cylinder screen cleaning, when the contact of the detection body 24A is detected by the detection switch 25A during cleaning, the rotation of the screw shaft 7 is stopped to end the cleaning. At this time, the outer cylinder screen end plate 18 gradually rotates, and the position of "a" becomes the side of the screen bottom surface 28. When starting the next dehydration operation in this state, the stopper 16a and the ratchet pawl 15b receive the frictional force acting in the opposite direction to the rotational force and rotational direction of the ratchet pawl 15a. After the outer cylinder screen end plate 18 gradually rotates in the forward rotation direction, the ratchet pawl 15b is locked to the stopper 16b1, and the outer cylinder screen 5 is fixed.

[0050] Subsequently, when locking the ratchet pawl 15b to the stopper 16b2 at the end of the second outer cylinder screen cleaning, when the contact of the detection body 24B is detected by the detection switch 25B during cleaning, the rotation of the screw shaft 7 is stopped to end the cleaning. At this time, the outer cylinder screen end plate 18 gradually rotates, and the position of "i" becomes the side of the screen bottom surface 28. When starting the next dehydration operation in this state, the stopper 16a and the ratchet pawl 15b receive the frictional force acting in the opposite direction to the rotational force and rotational direction of the ratchet pawl 15a. After the outer cylinder screen end plate 18 gradually rotates in the forward rotation direction, the ratchet pawl 15b is locked to the stopper 16b2, and the outer cylinder screen 5 is fixed.

[0051] Then, when locking the ratchet pawl 15b to the stopper 16b3 at the end of the third outer cylinder screen cleaning, when the contact of the detection body 24C is detected by the detection switch 25C during cleaning, the rotation of the screw shaft 7 is stopped to end the cleaning. At this time, the outer cylinder screen end plate 18 gradually rotates, and the position of "u" becomes the side of the screen bottom surface 28. When starting the next dehydration operation in this state, the stopper 16a and the ratchet pawl 15b receive the frictional force acting in the opposite direction to the rotational force and rotational direction of the ratchet pawl 15a. After the outer cylinder screen end plate 18 gradually rotates in the forward rotation direction, the ratchet pawl 15b is locked to the stopper 16b3, and the outer cylinder screen 5 is fixed.

[0052] Furthermore, when the ratchet pawl 15b is locked to the stopper 16b4 at the end of the fourth outer cylinder screen cleaning, if the contact of the detection body 24D is detected by the detection switch 25D during cleaning, the rotation of the screw shaft 7 is stopped to end the cleaning. At this time, the outer cylinder screen end plate 18 gradually rotates, and the position of "E" becomes closer to the screen bottom surface 28 side. When the next dehydration operation is started in this state, the stopper 16a and the ratchet pawl 15b are subject to the frictional force acting in the direction opposite to the rotational force and the rotational direction of the ratchet pawl 15a. After the outer cylinder screen end plate 18 gradually rotates in the forward rotation direction, the ratchet pawl 15b is locked to the stopper 16b4 and the outer cylinder screen 5 is fixed.

[0053] In this way, by sequentially changing the stopper 16b for locking the ratchet pawl 15b to 16b1, 16b2, 16b3, and 16b4, the position of the screen bottom surface 28 during the dehydration operation is sequentially shifted from the position of "A" to "I", "U", and "E". Therefore, the position of the screen bottom surface 28 during the dehydration operation is changed. That is, the locking position of the ratchet pawl 15 at the end of the outer cylinder screen cleaning determines the position of the screen bottom surface 28 during the next dehydration operation.

[0054] In this embodiment, the position of the screen bottom surface 28 is sequentially shifted as "A", "I", "U", and "E". However, as long as the position of the screen bottom surface 28 during the dehydration operation can be changed, it may be appropriately changed according to conditions, such as skipping "I" and changing in the order of "A", "U", and "E". Also, although four stoppers 16b are arranged at 90-degree intervals, at least two or more can be installed, and the installation interval is not limited either.

[0055] Figure 6 is a longitudinal side view of a screw press in another embodiment. In this embodiment, as shown in FIG. 2, the outer cylinder screen end plate 18 with the ratchet pawl 15b protruding therefrom and the plurality of stoppers 16b... are provided on the front frame 3 side. However, as shown in FIG. 6, these may be installed on the rear frame 4 side. In this case, the outer cylinder screen end plate 18A installed on the front frame 3 side is not formed with the ratchet pawl 15b.

[0056] The outer cylinder screen end plate 18B installed on the rear frame 4 side has a cylindrical shape similar to that of the outer cylinder screen end plate 18A, and extends from the end portion of the outer cylinder screen 5 toward the rear frame 4 side. The outer cylinder screen end plate 18B is formed with a ratchet pawl 15b (left hatched portion) protruding radially from the axis of the outer cylinder screen 5.

[0057] On the discharge side end face 4a of the rear frame 4, a plurality of stoppers 16b... (right hatched portion) are installed circumferentially at predetermined intervals, and the ratchet pawl 15b can be locked to any one of the stoppers 16b. Note that the ratchet pawl 15b (left hatched portion) on the rear frame 4 side, the ratchet pawl 15a (left hatched portion) on the front frame 3 side, the stopper 16a (right hatched portion), and the screw shaft end plate 17 have the same mechanism as in this embodiment.

[0058] When the screw shaft 7 rotates forward during the dehydration operation, the ratchet pawl 15a that rotates integrally with the screw shaft 7 rotates forward while pushing the stopper 16a outward. At this time, since the ratchet pawl 15b provided on the rear frame 4 side is in a state of being locked to any one of the stoppers 16b, the rotation of the outer cylinder screen 5 is inhibited.

[0059] On the other hand, when the screw shaft 7 rotates reversely during the cleaning of the outer cylinder screen, the ratchet pawl 15a on the front frame 3 side is locked to the stopper 16a, and the ratchet pawl 15b on the rear frame 4 side rotates reversely while pushing the plurality of stoppers 16b... outward. At this time, the outer cylinder screen end plate 18A on the front frame 3 side rotates reversely while rotating together with the screw shaft 7.

[0060] The present invention is not limited to the embodiments described in detail above. It can be appropriately modified and implemented without departing from the gist of the present invention.

Industrial Applicability

[0061] In the clogging prevention mechanism in the screw press of the present invention and the clogging prevention method using the same, since the position of the bottom surface of the screen during the dehydration operation is sequentially changed, local clogging does not occur in the outer cylinder screen. Since the cleaning time of the screen can be reduced, the operation time of the entire facility can be reduced, contributing to energy saving. Since the load on the outer cylinder screen is also reduced, it is excellent in maintainability.

Explanation of Signs

[0062] 5 Outer cylinder screen 6 Screw blade 7 Screw shaft 13 Cleaning pipe 15a, 15b Ratchet pawl 16a, 16b Stopper 17 Screw shaft end plate 18 Outer cylinder screen end plate 24 Sensing body 25 Detection switch 26 Detection device 28 Screen bottom surface

Claims

1. In a screw press, a screw shaft (7) with a screw blade (6) wound around a rotatably supported outer cylindrical screen (5) is installed inside, and raw liquid supplied to a start end side is filtered and dehydrated while being transported toward a terminal end side by the rotation of the screw shaft (7), and sludge adhering to the outer cylindrical screen (5) is removed by injecting a washing fluid from a washing pipe (13) onto the screen surface. a ratchet pawl (15a) that rotates integrally with the screw shaft (7) and protrudes radially from the center of the screw shaft (7); a stopper (16a) that is located on the rotation orbit of the ratchet pawl (15a), and that swings outward by the pressing force of the ratchet pawl (15a) during a dewatering operation, and that engages with the ratchet pawl (15a) during cleaning of the outer cylindrical screen, thereby rotating the outer cylindrical screen (5) integrally with the screw shaft (7); a ratchet claw (15b) which rotates integrally with the outer cylindrical screen (5) and protrudes radially from the center of the outer cylindrical screen (5); a plurality of stoppers (16b...) that are located on the rotation orbit of the ratchet pawl (15b), and that engage with the ratchet pawl (15b) during a dewatering operation to inhibit the rotation of the outer cylindrical screen (5), and that swing outward due to the pressing force of the ratchet pawl (15b) during cleaning of the outer cylindrical screen; and a detection device (26) for detecting that the stopper (16b) has swung outward due to the pressing force of the ratchet pawl (15b). A mechanism for preventing clogging in a screw press.

2. The screw shaft (7) The screw shaft end plate (17) is connected to the starting end, and the ratchet pawl (15a) protruding from the screw shaft end plate (17) is rotated integrally.

2. The mechanism for preventing clogging in a screw press according to claim 1.

3. The outer cylindrical screen (5) is An outer cylindrical screen end plate (18) is connected to the end, and the ratchet claw (15b) protruding from the outer cylindrical screen end plate (18) is rotated integrally with the ratchet claw (15a) engaged with the stopper (16a) provided on the outer cylindrical screen end plate (18).

3. The mechanism for preventing clogging in a screw press according to claim 2.

4. The detection device (26) The stopper (16b...) is provided with a detector (24) which is pushed up outward by a pressing force when the outer cylinder screen is washed, and the detector (24) is a contact or non-contact type detector switch (25) which detects the detector (24).

4. The mechanism for preventing clogging in a screw press according to claim 3.

5. By using the clogging prevention mechanism in the screw press according to any one of claims 1 to 4, During cleaning of the outer cylinder screen, a detection device (26) detects that each stopper (16b...) has received a pressing force from the ratchet claw (15b), and when it detects that a predetermined stopper (16b) has received the pressing force, the rotation of the screw shaft (7) is stopped; During dewatering operation, the ratchet claw (15b) is engaged with a desired stopper (16b) to change the position of the screen bottom surface (28) of the outer cylindrical screen (5). A method for preventing clogging in a screw press.

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