Contaminant Transfer Screen Device

Abstract

To provide an impurity transferring screen device for transferring impurities that cannot pass through gaps connecting the upstream side and the downstream side and block the gaps on the upstream side, and are contained in a liquid, upward on the upstream side, which is devised for gaps between fixed screen members and movable screen members.SOLUTION: A movable screen member 621 has a plurality of gap holding spacers 6212 projecting to adjacent fixed screen members 611 at an interval in a longitudinal direction. As for the gap holding spacers 6212, the projection end is brought into contact with the movable screen member 621, and the movable screen member 621 performs circulation operation, so that the projection end is slid with respect to the fixed screen members 611.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to an impurity transfer screen device that transfers impurities contained in a liquid, which cannot pass through the space connecting the upstream side and the downstream side and block the space on the upstream side, upward on the upstream side.

Background Art

[0002] As a device for separating impurities from waste liquid from factories, treated water such as industrial water and agricultural water, and sewage containing sludge or scum, a drum screen device that separates impurities and liquid through a rotating screen is known. This drum screen device has drawbacks such as the screen being easily clogged.

[0003] Therefore, the applicant of the present application has proposed an impurity transfer screen device in Patent Document 1 and Patent Document 2. This impurity transfer screen device includes a plurality of fixed screen members and a movable screen member disposed between these plurality of fixed screen members. The fixed screen members each extend obliquely upward, and the uppermost part protrudes from the water surface of the water tank. Further, the fixed screen members have a stepped shape in which a plurality of fixed step portions are arranged side by side in the extending direction. The movable screen member also extends obliquely upward and has a stepped shape in which a plurality of movable step portions are arranged side by side in the extending direction. The movable screen member transfers impurities toward the uppermost part of the fixed screen member by repeatedly moving upward and downward with respect to the fixed screen member. In the impurity transfer screen device described in Patent Document 1 and Patent Document 2, even if the space between the fixed screen member and the movable screen member is clogged by impurities captured without being able to pass through the space, when the movable screen member is moved, all the captured impurities immediately start to be transferred, so that clogging can be quickly eliminated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the foreign matter transfer screen device described above, the distance between the fixed screen member and the movable screen member is important.

[0006] In view of the above circumstances, an object of the present invention is to provide a foreign matter transfer screen device in which a device related to the distance between a fixed screen member and a movable screen member is devised.

Means for Solving the Problems

[0007] The foreign matter transfer screen device for solving the above object is In a foreign matter transfer screen device that cannot pass through the space connecting the upstream side and the downstream side and closes the space on the upstream side, and transfers the foreign matter contained in the liquid upward on the upstream side, a plurality of fixed screen members; a plurality of movable screen members that are arranged with a space from the fixed screen member between adjacent fixed screen members and transfer the foreign matter upward by performing a circulating operation; the movable screen member is provided with a plurality of space holding spacers that are spaced in the longitudinal direction and protrude toward adjacent fixed screen members, the space holding spacer has a protruding end that Fixed contacts the screen member, and the protruding end slides with respect to the fixed screen member when the movable screen member performs the circulating operation. The It is characterized in that.

[0008] Also, the movable screen member is made of resin, The spacer for maintaining the interval may be formed of a resin having higher abrasion resistance than the resin of the movable screen member.

[0009] Also, The fixed screen member has higher abrasion resistance than the spacer for maintaining the interval, The spacer for maintaining the interval may be characterized in that it is replaceable.

[0010] Also, The movable screen member may be characterized in that it is lighter than the fixed screen member but has lower rigidity.

Effect of the Invention

[0011] According to the present invention, it is possible to provide a foreign matter transfer screen device in which a device for the interval between the fixed screen member and the movable screen member is devised.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a diagram schematically showing a part of the facilities in a sewage treatment plant.

[0015] In this FIG. 1, a sedimentation tank 1, a raw sludge screen unit 2, a scum pit 3, and a scum screen unit 4 are shown.

[0016] The sedimentation tank 1 shown in Fig. 1 receives sewage (sewage) from one end side in the longitudinal direction (the left side in Fig. 1), settles the sludge contained in the received sewage at the bottom of the tank, and discharges water from the other end side (the right side in Fig. 1). Hereinafter, the left direction in Fig. 1 is referred to as the upstream, and the right direction in Fig. 1 is referred to as the downstream. A sludge pit 11 is provided at the bottom of the upstream side of the sedimentation tank 1, and a drain gutter 12 is installed near the water surface on the downstream side. In the sedimentation tank 1, the sludge settled at the bottom of the tank is collected in the sludge pit 11 by a sludge scraping machine (not shown). The sludge collected in the sludge pit 11 is sent by a sludge pump 13 to a raw sludge screen unit 2 installed outside the sedimentation tank 1. The sludge collected in the sludge pit 11 contains impurities such as scum. Hereinafter, the sewage containing sludge sent from the sludge pit 11 to the raw sludge screen unit 2 is referred to as raw sludge. The raw sludge screen unit 2 is provided with a raw sludge impurity transfer screen device 6. As will be described in detail later, the raw sludge impurity transfer screen device 6 captures the impurities contained in the raw sludge and transfers them in order to remove the impurities. The raw sludge from which the impurities have been removed by the raw sludge impurity transfer screen device 6 is then sent to a sludge thickening treatment facility or a sludge dewatering treatment facility. Also, in the sedimentation tank 1, the scum floating near the water surface is scraped by a scum scraping machine (not shown) to the drain gutter 12. The drain gutter 12 is connected to a scum pit 3, and the sewage containing scum (scum water) is collected in the scum pit 3, and then sent from the scum pit 3 by a scum pump 31 to a scum screen unit 4 installed outside the sedimentation tank 1. The scum water collected in the scum pit 3 also contains impurities such as scum. The scum screen unit 4 is provided with a scum impurity transfer screen device 7. The scum impurity transfer screen device 7 captures the scum, which is the impurity contained in the scum water, and transfers it in order to remove the impurity. The sewage from which the scum has been removed by the scum impurity transfer screen device 7 is returned to the sewage treatment plant.

[0017] Next, the sludge screen unit 2 provided with the sludge impurity transfer screen device 6 will be described as an example, but the scum screen unit 4 provided with the scum impurity transfer screen device 7 is the same. These sludge impurity transfer screen devices 6 and scum impurity transfer screen devices 7 both correspond to an example of an impurity transfer screen device.

[0018] Figure 2 is a front view of the sludge screen unit provided with the sludge impurity transfer screen device of the present embodiment.

[0019] As shown in Figure 2, the sludge screen unit 2 includes a water tank 5 and a sludge impurity transfer screen device 6. The sludge screen unit 2 shown in Figure 2 receives sludge from the left side of the figure (refer to the thick arrow in the figure). Hereinafter, the left side in Figure 2 is referred to as the upstream side, and the right side is referred to as the downstream side. Also, in Figure 2, the direction perpendicular to the plane of the paper is referred to as the width direction. The sludge impurity transfer screen device 6 includes a screen body 60, which will be described in detail later. In Figure 2, only the upstream side surface of the screen body 60 is shown by a thick dashed line.

[0020] In the lower half of the upstream side wall of the water tank 5 shown in Fig. 2, an inclined portion 51 is provided which is inclined downward on the downstream side toward the bottom 5a. In the lower half of the downstream side wall, an inclined portion 52 is provided which is inclined upward on the upstream side toward the bottom 5a. Therefore, the water tank 5 has a shape with a narrower bottom 5a side. This water tank 5 is a receiving tank that receives the sludge collected in the sludge pit 11 shown in Fig. 1 as raw sludge. An inflow pipe 53 is provided on the upstream side of the water tank 5. The raw sludge is supplied to the inflow pipe 53 by driving the sludge pump 13, flows into the water tank 5 from the tip 531 of this inflow pipe 53, and flows toward the downstream side (see the many thin arrows in the figure). Note that the tip 531 of the inflow pipe 53 is formed in a fan shape that expands as it goes toward the downstream side when viewed from above. Also, impurities X such as scum contained in the raw sludge are blocked by the screen body 60 provided in the raw sludge impurity transfer screen device 6 and are in a state of accumulating near the water surface on the upstream side of the screen body 60.

[0021] The raw sludge screen unit 2 is provided with an emergency overflow unit 54 upstream of the screen body 60 in the raw sludge impurity transfer screen device 6. Further, a drainage overflow unit 55 is provided downstream of the screen body 60. Both the emergency overflow unit 54 and the drainage overflow unit 55 have drainage troughs 541, 551 and weir plates 542, 552. These drainage troughs 541, 551 are all provided so as to project outward in the width direction of the water tank 5. The weir plate 552 of the drainage overflow unit 55 is provided at the boundary between the inside of the water tank 5 and the inside of the drainage trough 551. The inside of the water tank 5 and the inside of the drainage trough 551 are connected at a portion above the weir plate 552 and are not connected at a portion below the weir plate 552. When the water level of the water tank 5 exceeds the height position of the upper end of the weir plate 552, the sewage in the water tank 5 flows over the weir plate 552 and into the drainage trough 551. The sewage in the water tank 5 here is the raw sludge that has passed through the screen body 60, that is, the sewage containing the sludge from which impurities have been removed by the raw sludge impurity transfer screen device 6. This sewage is sent to the sludge thickening treatment facility and the sludge dewatering treatment facility, which are facilities in the post-treatment process. In this way, the raw sludge that has passed through the screen body 60 provided in the raw sludge impurity transfer screen device 6 is drained outside the raw sludge screen unit 2 by the drainage overflow unit 55.

[0022] The structure of the emergency overflow unit 54 is the same as that of the drainage overflow unit 55, but the emergency overflow unit 54 is provided at a higher position than the drainage overflow unit 55. When the raw sludge impurity transfer screen device 6 fails or the like, and the water level of the water tank 5 rises from the normal water level and exceeds the weir plate 542 of the emergency overflow unit 54, it flows into the drainage trough 541 of the emergency overflow unit 54. The raw sludge in the water tank 5 here is the raw sludge before passing through the screen body 60, that is, the sewage containing the sludge before impurities are removed by the raw sludge impurity transfer screen device 6. This sewage is returned to the upstream end of the raw sludge impurity transfer screen device 6.

[0023] Next, the raw sludge contaminant transfer screen device 6 will be described. The raw sludge contaminant transfer screen device 6 includes a screen body 60, a base frame 64, a drive mechanism 65, a control unit 66, and a chute 67. The screen body 60 is disposed inside the base frame 64, and the upper part of the base frame 64 is covered by a front cover 641 with a handle 6411. This front cover 641 is detachable from the base frame 64. The base frame 64 is made of stainless steel and is attached to a pair of support legs 69 fixed to the edge of the water tank 5. Although only one of the pair of support legs 69 is shown in FIG. 2, the other support leg 69 is fixed to the opposite edge of the water tank 5 with the raw sludge contaminant transfer screen device 6 sandwiched in the width direction. The base frame 64 and the support leg 69 are rotatably connected by a rotating shaft 69a and are fixed at the angle shown in FIG. 2 by bolts (not shown).

[0024] The drive mechanism 65 includes a motor 651 and a gear box (not shown). The gear box converts the driving force (rotational force) and the driving direction (rotational direction) generated by the motor 651. A drive shaft 652 (see FIG. 3) is connected to the gear box. The driving force generated by the motor 651 is transmitted to the drive shaft 652 via the gear box and acts as a force to rotate the drive shaft 652. The motor 651 is an inverter motor, and the control unit 66 performs rotational control of the motor 651 in response to a signal from a limit switch described later.

[0025] The screen body 60 is disposed in the water tank 5 in an inclined posture such that the lower part is located on the upstream side of the water tank 5 and the upper part is located on the downstream side. The uppermost part of this screen body 60 is located above the weir plate 542 of the emergency overflow unit 54. The impurities are captured by the screen body 60 and are gradually transferred toward the uppermost part along the longitudinal direction of the screen body 60 as will be described in detail later. The impurities that have reached the uppermost part of the screen body 60 are conveyed by a belt conveyor (not shown) to the inlet of the chute 67. The chute 67 has a discharge port 671 that opens outside the raw sludge impurity transfer screen device 6, and the impurities are discharged from the discharge port 671.

[0026] FIG. 3 is an exploded perspective view showing a part of the raw sludge impurity transfer screen device 6. In FIG. 3, the direction connecting the front right diagonal near side and the rear left diagonal far side of the drawing is the width direction of the raw sludge impurity transfer screen device 6.

[0027] In FIG. 3, the front cover 641 and the motor 651 of the drive mechanism 65 shown in FIG. 2 are removed from the raw sludge impurity transfer screen device 6, but the screen body 60 is shown. The screen body 60 is composed of a fixed unit 61 and a movable unit 62.

[0028] The fixed unit 61 has a plurality of pairs of fixed screen members 611 and also has a position regulating member 612 for the fixed screen that regulates the positions of the fixed screen members 611. On the other hand, the movable unit 62 has a plurality of movable screen members 621, a position regulating member 622 for the movable screen that regulates the positions of the movable screen members 621, and a pair of movable frames 623 to which the position regulating member 622 for the movable screen is attached. Each of the pair of movable frames 623 is made of stainless steel and is disposed outside the base frame 64. One of the movable frames 623 is shown on the front side of the paper in FIG. 3, while the other movable frame on the back side of the paper is mostly hidden by the base frame 64 and only a part of it is visible. The fixed unit 61 is not provided with a frame member such as this movable frame 623. The movable frame 623 is a triangular metal plate provided with two through holes 6231 and 6232. Due to the provision of the two through holes 6231 and 6232, the weight is reduced. As a result, the movable unit 62 having the movable frame 623 is reduced in weight.

[0029] Also, in FIG. 3, only one of the movable screen members 621 out of the plurality of movable screen members 621 provided in the width direction is shown. Further, FIG. 3 shows a spacer receiving portion 6112 provided on one of the fixed screen members 611 located behind the movable screen member 621 among the plurality of fixed screen members 611.

[0030] Also, FIG. 3 shows the drive shaft 652 of the drive mechanism 65. This drive shaft 652 is provided at a position eccentric from the central axis 6531 of the rotating plate 653. Receiving the rotational force of the motor 651 shown in FIG. 2, the drive shaft 652 rotates around the axis. As a result, the rotating plate 653 performs a rotational motion with the drive shaft 652 as the center of rotation. The rotating plate 653 is provided on both sides in the width direction, and the central axis 6531 connects the rotating plates 653 on both sides in the width direction. That is, the central axis 6531 extends in the width direction and performs a rotational motion together with the rotating plate 653. Movable frames 623 are fixed to both end portions of the central axis 6531, respectively.

[0031] FIG. 4 is a view showing a fixed screen member whose position is regulated by a fixed screen position regulating member and a movable screen member whose position is regulated by a movable screen position regulating member. Also in this FIG. 4, the direction connecting the front right obliquely in the drawing and the back left obliquely in the drawing is the width direction of the raw sludge contaminant transfer screen device 6.

[0032] A movable screen member 621 is positioned between a pair of fixed screen members 611, and the fixed screen members 611 and the movable screen member 621 are alternately arranged with a predetermined interval in the width direction. However, in FIG. 4, only some of the screen members are shown so that the fixed screen position regulating member 612 and the movable screen position regulating member 622 can be easily seen. That is, several fixed screen members 611 and several movable screen members 621 are shown in a part on one end side (front right obliquely) in the width direction, and one movable screen member 621 is shown on the other end side (back left obliquely) in the width direction. In the middle part in the width direction, both the fixed screen member 611 and the movable screen member 621 are omitted from the illustration. In this FIG. 4, movable screen members 621 are shown at both ends in the width direction.

[0033] As shown in FIG. 4, the position regulating members 622 for the movable screen are provided on both longitudinal sides of the movable screen member 621, respectively. In the position regulating members 622 for the movable screen, slits 6221 extending in the longitudinal direction are arranged side by side in the width direction. One movable screen member 621 is inserted into one slit 6221, and the interval between the two movable screen members 621 is maintained at a constant interval at each position on both longitudinal sides of the movable screen member 621 with the fixed screen member 611 positioned therebetween.

[0034] Further, the position regulating members 612 for the fixed screen are provided on both longitudinal sides of the fixed screen member 611, respectively. The position regulating members 612 for the fixed screen are provided outside the longitudinal direction (upper side or lower side) of the position regulating members 622 for the movable screen. In the position regulating members 612 for the fixed screen, slits 6121 extending in the longitudinal direction are also arranged side by side in the width direction. One fixed screen member 611 is inserted into one slit 6121, and the interval between adjacent fixed screen members 611 is maintained at a constant interval at each position on both longitudinal sides of the fixed screen member 611 with the movable screen member 621 positioned therebetween.

[0035] By the position regulating members 622 for the movable screen and the position regulating members 612 for the fixed screen described above, the interval in the width direction between the fixed screen member 611 and the movable screen member 621 is maintained at a predetermined interval. The predetermined interval is determined by the size of the foreign matter to be captured. For example, it may be 1 mm or less, or an interval between 1 mm and 3 mm, or an interval between 2 mm and 6 mm.

[0036] The position regulating members 612 for the fixed screen are fixed to the base frame 64 so as to span the side walls on both widthwise sides of the base frame 64 shown in FIG. 3.

[0037] In addition, a position regulating member 622 for the movable screen is fixed to the movable frame 623 so as to be bridged over the movable frames 623 shown in FIG. 3 provided on both sides in the width direction. And, as described above, since the movable frames 623 are fixed to both ends of the central axis 6531 extending in the width direction, when the drive shaft 652 rotates, the movable frames 623, the position regulating member 622 for the movable screen, and the movable screen member 621 inserted into the slit 6221 thereof perform a circulating operation in accordance with the rotation of the drive shaft 652.

[0038] FIG. 5(a) is a view showing the fixed screen member 611. The fixed screen member 611 is a member made of stainless steel with a thickness of 1.5 mm and extends about 2 m in the longitudinal direction. Also, the length in the height direction is about 100 mm.

[0039] A plurality of fixed step portions 6111 are continuously provided in the longitudinal direction on the fixed screen member 611 and are in a stepped shape. The fixed step portion 6111 is composed of a fixed step portion fg and a fixed mounting portion fs. Also, mounting pieces 6113 are provided on both sides in the longitudinal direction of the fixed screen member 611. These mounting pieces 6113 are inserted into the slit 6121 of the position regulating member 612 for the fixed screen shown in FIG. 4 and sandwich the position regulating member 612 for the fixed screen in the longitudinal direction. Further, between the mounting piece 6113 on one end side in the longitudinal direction (the lower left diagonal side in the figure) and the mounting piece 6113 on the other end side in the longitudinal direction (the upper right diagonal side in the figure), two spacer receiving portions 6112 are provided at intervals in the longitudinal direction. The mounting piece 6113 on one end side in the longitudinal direction, the spacer receiving portion 6112 on one end side in the longitudinal direction, the spacer receiving portion 6112 on the other end side in the longitudinal direction, and the mounting piece 6113 on the other end side in the longitudinal direction are located at equal intervals. The mounting piece 6113 protrudes downward in the height direction, and the spacer receiving portion 6112 also protrudes downward in the height direction.

[0040] The fixed screen member 611 shown in FIG. 5(a) is not provided with cutouts or through holes for the purpose of weight reduction.

[0041] FIG. 5(b) and FIG. 5(c) are diagrams showing the movable screen member.

[0042] There are two types of movable screen members 621 with different shapes. Due to the different shapes, their masses are also different. When distinguishing between the two, the movable screen member shown in FIG. 5(b) is referred to as the normal movable screen member 621N, and the movable screen member shown in FIG. 5(c) is referred to as the lightweight movable screen member 621L.

[0043] Both the normal movable screen member 621N shown in FIG. 5(b) and the lightweight movable screen member 621L shown in FIG. 5(c) have a plurality of movable step portions 6211 continuously provided in the longitudinal direction and are in a stepped shape. The movable step portion 6211 is composed of a movable step difference portion mg and a movable placement portion ms. Also, both the normal movable screen member 621N and the lightweight movable screen member 621L are members made of stainless steel with a thickness of 1.5 mm, similar to the fixed screen member 611 shown in FIG. 5(a), and extend about 2 m in the longitudinal direction. Also, the length in the height direction is about 100 mm. That is, the movable screen member 621 has the same thickness and the same length as the fixed screen member 611 and the same height. Note that the thickness, length, and height do not necessarily have to be exactly the same, but only approximately the same. However, the movable screen member 621 has the same number of movable step portions 6211 as the number of fixed step portions 6111 of the fixed screen member 611. Also, the length (height) of the movable step difference portion mg is the same as the length (height) of the fixed step difference portion fg, and the length (depth) of the movable placement portion ms is the same as the length (depth) of the fixed placement portion fs.

[0044] The lightweight movable screen member 621L shown in FIG. 5(c) is obtained by providing a notch CU in the normal movable screen member 621N shown in FIG. 5(b), and is lighter than the normal movable screen member 621N by the amount of the notch. This lightweight movable screen member 621L has a larger notch CU provided than the fixed screen member 611 shown in FIG. 5(a).

[0045] The normal movable screen member 621N and the lightweight movable screen member 621L are arranged alternately. That is, they are arranged side by side in the width direction in the order of the normal movable screen member 621N, the fixed screen member 611, the lightweight movable screen member 621L, the fixed screen member 611, the normal movable screen member 621N, and so on. Note that the movable screen members at both ends in the width direction may be the normal movable screen member 621N, and the remaining movable screen members may be the lightweight movable screen member 621L.

[0046] Also, the number of the normal movable screen members 621N and the number of the lightweight movable screen members 621L may be the same, or the number of the lightweight movable screen members 621L may be more than the number of the normal movable screen members 621N.

[0047] Due to the weight reduction by such lightweight movable screen members 621L, the total mass of the movable screen members 621 provided in the movable unit 62 becomes lighter than the total mass of the fixed screen members 611 provided in the fixed unit 61, and the raw sludge contaminant transfer screen device 6 can be driven with low power.

[0048] Note that a member having the same shape as the normal movable screen member 621N shown in FIG. 5(b) and made of a material having a specific gravity lighter than stainless steel may be used as the lightweight movable screen member. Examples of materials with a light specific gravity include various resin materials. Examples of materials with a light specific gravity and high strength include fiber reinforced plastic (FRP) and polyacetal resin. Also, a metal with a light specific gravity such as titanium or carbon fiber may be used.

[0049] Alternatively, instead of providing a cutout in the CU, through holes may be provided in the normal movable screen member 621N to reduce the weight. For example, a punching metal processed normal movable screen member 621N may be used as the weight-reduced movable screen member. Alternatively, the movable screen member 621 may have the same thickness and length as the fixed screen member 611 and the same height, but the thickness of the movable screen member 621 may be made thinner than that of the fixed screen member 611 while maintaining the same material to obtain a weight-reduced movable screen member. For example, the movable screen member 621 may have a thickness of 1.0 mm with respect to the fixed screen member 611 having a thickness of 1.5 mm. Alternatively, the length of the movable screen member 621 may be made shorter than that of the fixed screen member 611 to obtain a weight-reduced movable screen member, or the height of the movable screen member 621 may be made lower than that of the fixed screen member 611 to obtain a weight-reduced movable screen member.

[0050] The various weight reduction methods described above may be appropriately combined to form a weight-reduced movable screen member. For example, the movable screen member 621 may be made of resin and provided with a cutout in the CU. Further weight reduction can be achieved by combining multiple weight reduction methods. The number of weight-reduced movable screen members 621L may be equal to or more than the number of normal movable screen members 621N, but in this case, it may also be less than the number of normal movable screen members 621N.

[0051] Furthermore, all of the movable screen members 621 included in the movable unit 62 may be the lightweight movable screen members described above. In this case, lightweight movable screen members with different weight reduction methods may be mixed and used. For example, lightweight movable screen members made of different materials may be used. More specifically, they may be arranged side by side in the width direction in the order of a resin-made lightweight movable screen member, the fixed screen member 611, a titanium-made lightweight movable screen member, the fixed screen member 611, a resin-made lightweight movable screen member, and so on. Alternatively, lightweight movable screen members with different shapes may be used. More specifically, they may be arranged side by side in the width direction in the order of a resin-made lightweight movable screen member having the same shape as the normal movable screen member 621N shown in FIG. 5(b), the fixed screen member 611, the lightweight movable screen member 621L shown in FIG. 5(c), the fixed screen member 611, a resin-made lightweight movable screen member, and so on.

[0052] Also, attachment pieces 6213 are provided on both sides in the longitudinal direction of the movable screen member 621. These attachment pieces 6213 are inserted into the slits 6221 of the movable screen position regulating member 622 shown in FIG. 4 and sandwich the movable screen position regulating member 622 in the longitudinal direction.

[0053] Furthermore, the movable screen member 621 is provided with four spacers 6212 for maintaining intervals, which protrude on both sides in the thickness direction, at four locations spaced apart in the longitudinal direction. In the lightweight movable screen member 621L shown in FIG. 5(c), a notch CU is provided so as to leave the periphery of the spacer 6212 for maintaining intervals provided between the two attachment pieces 6213. The spacer 6212 for maintaining intervals protrudes toward the adjacent fixed screen member 611. That is, the spacer 6212 for maintaining intervals provided on one end side in the longitudinal direction rather than the attachment piece 6213 protrudes toward the base of the attachment piece 6113 provided on one end side in the longitudinal direction of the fixed screen member 611. Also, the spacer 6212 for maintaining intervals adjacent to the spacer 6212 protrudes toward the spacer receiving portion 6112 on one end side in the longitudinal direction of the fixed screen member 611. On the other hand, the spacer 6212 for maintaining intervals provided on the other end side in the longitudinal direction rather than the attachment piece 6213 protrudes toward the base of the attachment piece 6113 provided on the other end side in the longitudinal direction of the fixed screen member 611. Also, the spacer 6212 for maintaining intervals adjacent to the spacer 6212 protrudes toward the spacer receiving portion 6112 on the other end side in the longitudinal direction of the fixed screen member 611. When the movable screen member 621 performs a circulating operation, each spacer 6212 for maintaining intervals slides with respect to the fixed screen member 611 in an annular locus at a position protruding toward the fixed screen member 611. The locus is shown by a gray line in the fixed screen member 611 shown in FIG. 5(a). The spacer 6212 for maintaining intervals is formed of a wear-resistant resin. For example, when the movable screen member 621 is made of resin, it is formed of a resin having higher wear resistance than the resin of the movable screen member 621.

[0054] FIG. 6(a) is an enlarged partial cross-sectional view of a cross-section of the periphery of one of the four spacers for maintaining intervals.

[0055] The members with cross-hatching shown above and below are fixed screen members 611, and the member with downward-left hatching shown between them is the movable screen member 621. The spacer 6212 for maintaining the interval is a combination of a male part mp and a female part fp. The male part mp has a hemispherical head mp1, a leg part mp2 extending from the head mp1, and a locking part mp3 provided at the tip of the leg part mp2. The leg part mp2 has a length equal to or greater than the thickness of the movable screen member 621. This leg part mp2 is inserted into a mounting hole 621h provided in the movable screen member 621 and penetrates the movable screen member 621. The female part fp is hemispherical and has a locking hole fp1 into which the locking part mp3 of the male part mp fits. The edge defining the locking hole fp1 of the female part fp and the locking part mp3 of the male part mp elastically deform with each other when the locking part mp3 is inserted into the locking hole fp1, and after the locking part mp3 enters the locking hole fp1, the edge of the locking hole fp1 and the locking part mp3 are locked to fix the spacer 6212 for maintaining the interval to the movable screen member 621. The head mp1 of the male part mp contacts the fixed screen member 611 shown above, and the interval between the movable screen member 621 to which the spacer 6212 for maintaining the interval is attached and the fixed screen member 611 shown above is maintained at a predetermined interval W. Also, the female part fp contacts the fixed screen member 611 shown below, and the interval between the movable screen member 621 to which the spacer 6212 for maintaining the interval is attached and the fixed screen member 611 shown below is also maintained at the predetermined interval W.

[0056] Also, the movable screen member 621 is reinforced by the spacer 6212 for maintaining the interval. In particular, the reinforcement by the spacer 6212 for maintaining the interval is effective for a resin-made movable screen member or a movable screen member with a small thickness.

[0057] The fixed screen member 611 has higher wear resistance than the spacer 6212 for maintaining the interval, and the spacer 6212 for maintaining the interval is replaceable. Note that screw holes may be provided in the movable screen member 621, and the spacer 6212 for maintaining the interval may be screwed into the screw holes. In this case, the spacer 6212 for maintaining the interval can be made of a metal with higher wear resistance.

[0058] In addition, the shape of the head mp1 of the male part mp and the female part fp may be a shape that makes point contact or line contact with the fixed screen member 611, other than the hemispherical shape, and may be a shape composed of a curved surface, or a shape combined with a plane.

[0059] Note that arranging the movable screen member 621 and / or the fixed screen member 611 with tension applied in the longitudinal direction can prevent the screen member from bending, and is also effective when maintaining the interval between the movable screen member 621 and the fixed screen member 611 at a predetermined interval W.

[0060] FIG. 6(b) is a diagram showing a modified example of the movable frame shown in FIG. 3.

[0061] The movable frame 623 shown in FIG. 3 had two through holes provided, but the movable frame 623' in this modified example has, in addition to the hole 653h to which the central axis 6531 shown in FIG. 3 is attached, one through hole 6233 provided, and one notch 6234 also provided. The movable frame 623' shown in FIG. 6(b) is lightened by the through hole 6233 and the notch 6234. Note that the movable frame 623 may be lightened by punching metal. Alternatively, it may be lightened by changing to a material with a low specific gravity. Furthermore, these weight reduction methods may be combined for even more weight reduction.

[0062] Subsequently, the drive of the raw sludge contaminant transfer screen device 6 will be described.

[0063] Fig. 7(a) is a schematic view of the screen member provided in the impurity removal screen device as seen from the upstream side of the water tank.

[0064] As shown in this Fig. 7(a), the fixed screen member 611 and the movable screen member 621 are alternately arranged at a predetermined interval W over the entire width of the water tank 5. In Fig. 7(a), in order to simplify the drawing, the screen members in the central part in the width direction are omitted. The predetermined interval W is an interval connecting the upstream side and the downstream side, which is set based on the balance between the flow rate of the raw sludge passing through the raw sludge impurity transfer screen device 6 and the size of the device. For example, it is an interval of 2 mm or more and 6 mm or less. In this Fig. 7(a), in order to clearly show the fixed step portion 6111 and the movable step portion 6211, the thicknesses of the fixed screen member 611 and the movable screen member 621 are shown with considerable exaggeration. The thickness of both the fixed screen member 611 and the movable screen member 621 is 1.5 mm, and when the predetermined interval W is 2 mm or more and 6 mm or less, they are thinner than the predetermined interval W.

[0065] The fixed screen member 611 is fixed in a state where its lower end is located above the bottom 5a of the water tank 5. On the other hand, the movable screen member 621 moves up and down between a pair of fixed screen members 611. The movable screen member 621 shown in Fig. 6 is located above the fixed screen member 611. As a result, the fixed step portion 6111 and the movable step portion 6211 are displaced in the height direction and are not aligned in the height direction. That is, the height positions of the fixed placement portion fs and the movable placement portion ms are displaced.

[0066] Fig. 7(b) is a diagram for explaining the circulation operation of the movable step portion.

[0067] As described above, since the movable frames 623 are fixed to both ends of the central axis 6531 extending in the width direction, when the drive shaft 652 rotates, the movable screen member 621 performs a circulating operation in accordance with the rotation of the drive shaft 652. The two-dot chain line shown in Fig. 7(b) indicates the locus r of the upstream end mst of the movable placement part ms when the movable screen member 621 performs a circulating operation. This locus r is a circular locus with a straight line connecting the upstream ends mst of the vertically adjacent movable placement parts ms as the diameter. For example, it is a circular locus with a straight line connecting the upstream end mst of the movable placement part ms in the first-stage movable stage part 6211 and the upstream end mst of the movable placement part ms in the second-stage movable stage part 6211 as the diameter.

[0068] Fig. 8 is a diagram showing step by step the state of the first half of transferring impurities upward by the impurity transfer screen device for raw sludge, and Fig. 9 is a diagram showing step by step the state of the second half following Fig. 8.

[0069] Above Figs. 8 and 9, schematic diagrams showing the fixed screen member 611 and the movable screen member 621 from the width direction (side) are shown step by step from left to right (Figs. 8(a-1) to 8(a-4), Figs. 9(a-5) to 9(a-8)). In addition, in each of Figs. 8(a-1) to 8(a-4) and Figs. 9(a-5) to 9(a-8), the drive shaft 652 rotating around the axis, the rotating plate 653 performing a rotating operation with the drive shaft 652 as the rotation center, and the central axis 6531 for circulating the movable screen member 621 are also shown. The central axis 6531 rotates clockwise around the drive shaft 652 as indicated by the arrow in each figure. The rotation angle of this central axis 6531 is for reference.

[0070] Below each of the figures in FIGS. 8(a-1) to 8(a-4) and FIGS. 9(a-5) to 9(a-7), there is shown a schematic diagram representing, from directly above, the fixed placement portion (here, the fixed placement portion fs_2 in the second fixed step portion 6111 from the bottom) in a specific fixed step portion where the number of steps is aligned between the fixed screen member 611 and the movable screen member 621, and the movable placement portion (here, the movable placement portion ms_2 in the second movable step portion 6211 from the bottom) in a specific movable step portion (FIGS. 8(b-1) to 8(b-4), FIGS. 9(b-5) to 9(b-7)). Further, below FIG. 9(a-8), there is shown a schematic diagram representing, from directly above, the fixed placement portion (here, the fixed placement portion fs_2 in the second fixed step portion 6111 from the bottom) in the above-mentioned specific fixed step portion and the movable placement portion (here, the movable placement portion ms_1 in the first movable step portion 6211 which is the bottommost) in a movable step portion one step lower than the above-mentioned specific movable step portion (FIG. 9(b-8)). In the schematic diagram representing from directly above shown below, similar to FIG. 7(a), the thicknesses of the fixed screen member 611 and the movable screen member 621 are shown with considerable exaggeration. Also, in the schematic diagram shown below, the movable step portion is shown in gray. The figures shown above and the figures shown below correspond in a one-to-one relationship.

[0071] In the schematic diagram representing from the width direction shown above, raw sludge flows in from the left side of the figure and flows toward the right side as indicated by the white arrow. Therefore, the left side of the figure is the upstream side and the right side is the downstream side. On the other hand, in the schematic diagram representing from directly above shown below, raw sludge flows in from the upper side of the figure and flows toward the lower side as indicated by the white arrow. Therefore, the upper side of the figure is the upstream side and the lower side is the downstream side.

[0072] The state of the movable screen member 621 shown in Fig. 8(a-1) is the same as the state of the movable screen member 621 shown in Fig. 7. As shown in Fig. 8(a-1), the movable screen member 621 is located above the fixed screen member 611. Therefore, when comparing the fixed step portions 6111 and the movable step portions 6211 with the same number of steps, the movable step portions 6211 are at a higher position. For example, between the fixed placement portion fs_1 in the first-stage fixed step portion 6111 at the lowermost stage and the fixed placement portion fs_2 in the second-stage fixed step portion 6111 from the bottom, the movable placement portion ms_1 in the first-stage movable step portion 6211 at the lowermost stage is located.

[0073] Also, as shown in Fig. 8(a-1), the movable screen member 621 is located on the downstream side of the fixed screen member 611. That is, the fixed screen member 611 with a fixed position is relatively located on the upstream side, and the movable screen member 621 is in a retracted state where it has retreated to the downstream side of the fixed screen member 611. The relationship between the fixed placement portion fs_2 in the second-stage fixed step portion 6111 from the bottom with a different height position and the movable placement portion ms_2 in the second-stage movable step portion 6211 from the bottom is also such that the movable placement portion ms_2 is located on the downstream side, as shown in Fig. 8(b-1).

[0074] Fig. 8(a-1) schematically shows a state in which the rod-shaped foreign matter X1 is captured horizontally on the fixed placement portion fs of the fixed screen member 611. Since the thickness of the fixed screen member 611 is 1.5 mm, actually, the rod-shaped foreign matter X1 is placed horizontally across the fixed placement portions fs of the plurality of fixed screen members 611. Also, a state in which the string-shaped foreign matter X2 has entered and been captured on the movable placement portion ms of the movable screen member 621 that has retreated to the downstream side is also schematically shown. Since the thickness of the movable screen member 621 is also 1.5 mm and it is the string-shaped foreign matter X2, actually, it is captured so as to be caught on a plurality of placement portions such as the movable placement portion ms, the fixed placement portion fs beside it, and the movable placement portion ms beside it.

[0075] The movable screen member 621 performs a circulating operation in accordance with the rotation of the drive shaft 652 shown in FIG. 3, which is caused by the rotation of the motor 651 shown in FIG. 2. That is, the movable screen member 621 performs an operation of alternately repeating an advanced state in which it advances upstream of the pair of fixed screen members 611, 611 between the pair of fixed screen members 611, 611 and a retracted state in which it retreats downstream of the pair of fixed screen members 611, 611.

[0076] The movable screen member 621 shown in FIG. 8(a-1) moves downward and also moves downstream. As a result, as shown in FIG. 8(a-2), the movable screen member 621 reaches the state where it retreats the most downstream during the circulating operation. In this state, as shown in FIG. 8(a-2), the movable screen member 621 has descended to the same height position as the fixed screen member 611. Also, as shown in FIG. 8(b-2), regarding the relationship between the fixed placement portion fs_2 in the second fixed step portion 6111 from the bottom and the movable placement portion ms_2 in the second movable step portion 6211 also from the bottom, the movable placement portion ms_2 retreats more downstream.

[0077] The movable screen member 621 in the state where it has retreated the most continues the circulating operation, continues to move downward, and at the same time starts to move upstream. As a result, as shown in FIG. 8(a-3), the movable screen member 621 reaches the state where it moves the most downward during the circulating operation. In this state, as shown in FIG. 8(a-3), the movable screen member 621 is located below the fixed screen member 611.

[0078] The movable screen member 621 that has moved to the lowest position continues the circulation operation, keeps moving toward the upstream side, and at the same time starts to move upward. As a result, as shown in FIG. 8(a-4), the movable screen member 621 rises to the same height position as the fixed screen member 611. When viewed in the width direction, the movable screen member 621 overlaps the fixed screen member 611, and the fixed step portion 6111 and the movable step portion 6211 are aligned in the same number of steps. For example, the fixed placement portion fs_2 in the second fixed step portion 6111 from the bottom aligns with the movable placement portion ms_2 in the second movable step portion 6211 from the bottom. The rod-shaped contaminants X1 placed on the plurality of fixed placement portions fs will also be placed on the movable placement portions ms located between these fixed placement portions fs. Also, as shown in FIG. 8(b-4), the movable placement portion ms_2 in the second movable step portion 6211 from the bottom is aligned with the fixed placement portion fs_2 in the second fixed step portion 6111 from the bottom in the advancing and retreating direction (upstream and downstream direction). When viewed as a whole for the movable screen member 621, the movable screen member 621 shown in FIG. 8(a-4) neither advances to the upstream side nor retreats to the downstream side beyond the fixed screen member 611, and is in a parallel state aligned with the fixed screen member 611 in the advancing and retreating direction (upstream and downstream direction). Hereinafter, the parallel state in which the fixed step portion 6111 and the movable step portion 6211 are aligned in the same number of steps is referred to as a parallel state with the same number of steps.

[0079] The movable screen member 621 increases its moving speed from the time when it enters the parallel state with the same number of steps shown in FIG. 8(a-4). The rotating plate 653 is provided with a first limit switch (not shown) for detecting the central axis 6531 (the central axis 6531 shown in FIG. 8(a-4)) when it enters the parallel state with the same number of steps. The control unit 66 receives the detection signal from the first limit switch and controls the inverter to increase the rotation speed of the motor 651. That is, when the movable screen member 621 enters the parallel state with the same number of steps, the rotation speed of the motor 651 is increased. The movable screen member 621 shown in FIG. 8(a-4) moves further upward and toward the upstream side at an increased moving speed. The driving of such a movable screen member 621 is referred to as normal driving, and the driving until then is referred to as low-speed driving.

[0080] Normally driven, the movable screen member 621 begins to advance upstream of the fixed screen member 611 and enters the advanced state (Fig. 9(a-5)). Also, as shown in Fig. 9(b-5), the relationship between the fixed placement portion fs_2 in the second fixed step portion 6111 from the bottom and the movable placement portion ms_2 in the second movable step portion 6211 from the bottom is such that the movable placement portion ms_2 has advanced upstream.

[0081] Furthermore, the movable screen member 621 in the advanced state is located above the fixed screen member 611. That is, when comparing the fixed step portion 6111 and the movable step portion 6211 with the same number of steps, the movable step portion 6211 is at a higher position. For example, the movable placement portion ms_2 in the second movable step portion 6211 from the bottom is at a higher position than the fixed placement portion fs_2 in the second fixed step portion from the bottom. Also, as shown in Fig. 9(a-5), the block-shaped foreign matter X3 floating near the water surface is captured by the movable step portion 6211 that has advanced upstream of the fixed step portion 6111. Both the string-shaped foreign matter X2 and the block-shaped foreign matter X3 are transferred upward by the movable step portion 6211.

[0082] When the circulation operation is further continued by normal driving upward and upstream, as shown in Fig. 9(a-6), the movable screen member 621 reaches the state where it has advanced the most upstream during the circulation operation. Also, as shown in Fig. 9(b-6), the relationship between the fixed placement portion fs_2 in the second fixed step portion 6111 from the bottom and the movable placement portion ms_2 in the second movable step portion 6211 from the bottom is such that the movable placement portion ms_2 has advanced upstream.

[0083] The movable screen member 621 in the state where it has advanced the most continues the circulation operation and continues to move upward while starting to move downstream. As a result, as shown in Fig. 9(a-7), the movable screen member 621 reaches the state where it has moved the most upward during the circulation operation.

[0084] The movable screen member 621, which has moved to the uppermost position, continues the circulating operation, and as shown in FIG. 9(a-8), the movable screen member 621 is aligned with the fixed screen member 611 in the forward and backward direction again. However, in the parallel state shown in FIG. 9(a-8), the fixed step 6111 has risen to the height position of the movable step 6211 one step above. For example, the height position of the first movable step 6211 coincides with the height position of the fixed step 6111 in the second step. As shown in FIG. 9(b-8), the fixed placement part fs_2 in the second fixed step 6111 from the bottom and the movable placement part ms_1 in the first movable step 6211, which is the lowest step and coincides with the fixed placement part fs_2 in the height direction, are aligned in the forward and backward direction (upstream and downstream directions). Hereinafter, the parallel state in which the movable step 6211 is aligned with the fixed step 6111 one step above will be referred to as a parallel state one step above.

[0085] The rod-shaped impurities X1 that have been placed on the multiple movable placement parts ms and transferred upward are also placed on the fixed placement part fs one step above. The string-shaped impurities X2 are also caught on the fixed placement part fs one step above, and the clump-shaped impurities X3 are also placed on the fixed placement part fs one step above. The movable screen member 621 continues to move further downward and downstream, but even as the movable screen member 621 moves, the rod-shaped impurities X1, the string-shaped impurities X2, and the clump-shaped impurities X3 all remain on the fixed placement part fs one step above, and are transferred to the fixed step part 6111 (fixed placement part fs) one step above.

[0086] The moving screen member 621 decreases in moving speed from the time when it reaches the stepped parallel state shown in Fig. 9(a-8). The rotating plate 653 is also provided with a second limit switch (not shown) for detecting the central axis 6531 (the central axis 6531 shown in Fig. 8(a-8)) when it reaches the stepped parallel state. The control unit 66 receives the detection signal from the second limit switch and controls the inverter to reduce the rotation speed of the motor 651. That is, when the moving screen member 621 reaches the stepped parallel state, the rotation speed of the motor 651 decreases, and the drive is switched from normal drive to low-speed drive. The moving screen member 621 shown in Fig. 9(a-8) further moves downward and downstream by low-speed drive. As a result, the moving screen member 621 shown in Fig. 9(a-8) returns to the same state as the moving screen member 621 shown in Fig. 8(a-1), and one cycle of the circulating operation of the moving screen member 621 is completed.

[0087] As described above, the contaminants X1 to X3 are transferred step by step upward to the fixed step portion 6111 (fixed placement portion fs), and finally reach the uppermost fixed step portion 6111 (fixed placement portion fs) of the fixed screen member 611. That is, the contaminants X1 to X3 are transferred stepwise along the longitudinal direction of the fixed screen member 611. The contaminants X1 to X3 that have reached the uppermost fixed step portion 6111 (fixed placement portion fs) are transported to the inlet of the chute 67 shown in Fig. 2 by a belt conveyor (not shown) as described above, and are discharged out of the raw sludge contaminant transfer screen device 6 from the discharge port 671 of the chute 67.

[0088] In this embodiment, the movable screen member 621 continues its circulating operation without stopping. During this circulating operation, the period when the movable screen member 621 is in the retracted state is a low-speed drive with a relatively low transfer speed, and the period when the movable screen member 621 is in the extended state is a normal drive with a relatively high transfer speed. The received raw sludge may contain hard impurities such as pieces of driftwood. When such hard impurities hit the movable screen member 621, there is a risk that the drive mechanism 65 (see FIG. 2), such as a gearbox, may be damaged by the impact. However, in the raw sludge impurity transfer screen device 6 of this embodiment, the period during which the movable screen member 621 is on the downstream side of the fixed screen member 611 can be made relatively long, reducing the risk of the flowing-in hard impurities hitting the movable screen member 621. As a result, the risk of the drive mechanism 65 being damaged is reduced.

[0089] It also protects the movable screen member 621. That is, the number of times the hard impurities are received by the fixed screen member 611 increases, and the number of times received by the movable screen member 621 decreases, reducing the risk of the movable screen member 621 wearing, deforming, or being damaged. For example, in the state shown in FIG. 8(a-1), the string-like impurity X2 deforms due to its softness and hits the movable screen member 621, but there is no problem because it is soft. The rod-like impurity X1 is received by the fixed screen member 611 and does not hit the movable screen member 621. The movable screen member 621 is prone to wear in the first place due to its circulating operation, and it is necessary to protect the movable screen member 621 as much as possible. In addition, when the movable screen member 621 is the lightweight movable screen member 621L, the lightweight movable screen member 621L is often lower in strength than the movable screen member 621, which is particularly effective. For example, this is the case when a resin-made lightweight movable screen member 621L is used instead of a metal-made movable screen member 621.

[0090] Note that the switching between low-speed drive and normal drive is performed by inverter control based on a detection signal from a limit switch that detects the parallel state of the movable screen member 621. However, a stepping motor may be used as the motor 651, and the rotational speed of the stepping motor may be controlled based on the number of steps from the reference position of the movable screen member 621.

[0091] Also, it may be an aspect in which the movable screen member 621 stops for a predetermined period during the period when it is in the retracted state (the state from beyond Fig. 9(a-8) to Fig. 8(a-4)). In this aspect, the control unit 66 may stop the rotation of the motor 651 for a predetermined period after a predetermined time has elapsed since receiving the detection signal from the second limit switch, or a third limit switch for detecting the central axis 6531 when the movable screen member 621 reaches a predetermined position may be provided, and the rotation of the motor 651 may be stopped for a predetermined period when the detection signal of the third limit switch is received. The predetermined position will be described in detail below.

[0092] The stop position where the movable screen member 621 stops for a predetermined period may be the position where the movable screen member 621 has retracted most to the downstream side (Fig. 8(a-2)). If it stops at this position, the risk of hard foreign matter hitting the stopped movable screen member 621 can be further reduced. However, when it stops for a long time, due to the fact that the movable stage portion 6211 has retracted to the downstream side with respect to the fixed stage portion 6111, the depression (the depression that is recessed toward the downstream side) between the fixed stage portion 6111 and the movable stage portion 6211 is deep, and it is conceivable that foreign matter will accumulate in this depression. Therefore, a short-time stop is preferable.

[0093] Further, the stop position may be a position where the movable screen member 621 has moved downstream after being in the raised parallel state. That is, it may be a position between when the movable screen member 621 changes from the position in Fig. 9(a-8) to the position in Fig. 8(a-1). When stopped at this position, when the movable screen member 621 starts to move, an initial movement using potential energy becomes possible. Further, the stop position is preferably a position immediately after the movable screen member 621 has entered the raised parallel state. That is, it is preferably near the position in Fig. 9(a-8). By doing so, more potential energy can be utilized. In other words, it is preferable that the distance of movement downward from the stopped state be as long as possible to gain momentum for the movable screen member 621. Also, it is preferable that the above-mentioned depression between the fixed step portion 6111 and the movable step portion 6211 be shallow, reducing the accumulation of debris in this depression.

[0094] Alternatively, the stop position may be a position where the movable screen member 621 has moved upward from the lowest position. That is, it may be a position between when the movable screen member 621 changes from the position in Fig. 8(a-3) to the position in Fig. 8(a-4). When stopped at this position, when the movable screen member 621 starts to move, the transfer of debris upward can be started at an early timing. Further, the stop position is preferably a position immediately before the movable screen member 621 enters the parallel state where the number of steps matches. That is, it is preferably near the position in Fig. 8(a-4). By doing so, the transfer of debris upward can be started at an earlier timing. Also here, the above-mentioned depression between the fixed step portion 6111 and the movable step portion 6211 becomes shallow, reducing the accumulation of debris in this depression, which is preferable.

[0095] The stop position described above corresponds to the home position of the movable screen member 621.

[0096] The movable screen member that has stopped at the home position moves at a constant speed (normal drive) while starting to move and performing a circulation operation. By doing so, the period during which the movable screen member 621 is downstream of the fixed screen member 611 can be made relatively long, reducing the risk of hitting hard foreign matter and decreasing the likelihood of damage to the drive mechanism 65 and the movable screen member 621. Even when the movable screen member 621 is stopped for a predetermined period, during the circulation operation, normal drive and low-speed drive may be combined as described with reference to FIG. 8.

[0097] Also, the movable screen member 621 may repeatedly execute a circulation operation while receiving a processing liquid such as raw sludge in the water tank 5 (while the liquid is flowing in), and stop at the home position after stopping the reception of the processing liquid (when the inflow of the liquid has ended). Alternatively, the movable screen member 621 may stop at the home position after performing the circulation operation a predetermined number of times, or may stop at the home position after performing the circulation operation for a predetermined time, or may necessarily stop at the home position for each circulation operation.

[0098] Also, in the present embodiment, the movable screen member 621 repeats a circulation operation such as the maximum retracted state (FIG. 8(a-2)), the parallel state with the same number of steps (FIG. 8(a-4)), the maximum advanced state (FIG. 9(a-6)), the parallel state one step up (FIG. 9(a-8)), the maximum retracted state (FIG. 8(a-2))... However, a so-called reverse rotation circulation operation such as the maximum retracted state (FIG. 8(a-2)), the parallel state one step up (FIG. 9(a-8)), the maximum advanced state (FIG. 9(a-6)), the parallel state with the same number of steps (FIG. 8(a-4)), the maximum retracted state (FIG. 8(a-2))... may be repeated. Even when performing a reverse rotation circulation operation, the period during which the movable screen member 621 is downstream of the fixed screen member 611 is made relatively long. In the reverse rotation circulation operation, the movable screen member 621 moves upward in the retracted state.

[0099] Also, although the movable unit 62 is heavier than the fixed unit 61 by the weight of the movable frame 623, in addition to the weight reduction of the movable frame 623 by the through holes 6231 and 6232 shown in FIG. 3, the movable frame 623 is made of a material with a specific gravity lighter than stainless steel, and by further reducing the weight, the movable unit 62 can be made lighter than the fixed unit 61, and the raw sludge contaminated material transfer screen device 6 can be driven with lower power. As materials with a light specific gravity, various resin materials can be mentioned. As those with a light specific gravity and high strength, fiber reinforced plastic (FRP) and polyacetal resin can be mentioned. Also, a metal with a light specific gravity such as titanium or carbon fiber may be used.

[0100] Furthermore, by making the position regulation of the movable screen member 621 by the movable screen position regulating member 622 stronger, applying tension to the movable screen member 621 as described above, or increasing the strength of the movable screen member 621, and connecting the movable screen position regulating member 622 on the drive shaft 652 side shown in FIG. 2 to the drive shaft 652, the movable frame 623 can be omitted, and the weight reduction of the movable unit 62 can be further advanced.

[0101] Note that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope described in the claims. For example, although the raw sludge contaminated material transfer screen device 6 has been described as an example, the present invention can be applied not only to sewage treatment facilities but also to facilities for treating water such as industrial water and agricultural water, and facilities for treating liquids such as waste liquids.

[0102] Hereinafter, an appended note including what has been described so far is provided.

[0103] (Appended Note A) In a contaminated material transfer screen device that transfers contaminants contained in a liquid, which cannot pass through the interval connecting the upstream side and the downstream side and closes the interval on the upstream side, upward on the upstream side, a plurality of fixed screen members and A plurality of movable screen members are arranged with a space between adjacent fixed screen members, and move upward to transfer the contaminants upward. A contaminant transfer screen device, characterized in that the mass of all the movable screen members of the contaminant transfer screen device is lighter than the mass of all the fixed screen members of the contaminant transfer screen device.

[0104] (Appendix B) The contaminant transfer screen device according to Appendix A, characterized in that the plurality of movable screen members include those made of a material having a specific gravity lighter than that of the material of the fixed screen member.

[0105] (Appendix C) The contaminant transfer screen device according to Appendix A or B, characterized in that the plurality of movable screen members include those provided with notches or through-holes larger than those of the fixed screen members.

[0106] (Appendix D) A movable frame, A movable screen regulating member attached to the movable frame to regulate the positions of the plurality of movable screen members. The plurality of movable screen members move together with the movable frame and the movable screen regulating member. The contaminant transfer screen device according to any one of Appendices A to C, characterized in that the movable frame is provided with a notch or a through-hole.

[0107] (Appendix 1-1) In a contaminant transfer screen device including a screen body having a space connecting the upstream side and the downstream side, and transferring contaminants contained in a liquid, which cannot pass through the space and block the space on the upstream side of the screen body, upward on the upstream side of the screen body, The screen body is A pair of fixed screen members, The motor rotates to perform a circulation operation in which the advancing state in which it advances upstream of the pair of fixed screen members and the retracting state in which it retreats downstream of the pair of fixed screen members are alternately repeated, and when in either the advancing state or the retracting state, it moves upward to transfer the contaminants upward, and is provided with a movable screen member that moves downward in the other state. The movable screen member performs the circulation operation by controlling the rotational speed of the motor so that the time in the retracting state is longer than the time in the advancing state, and the time in the retracting state is longer than the time in the parallel state in which the pair of fixed screen members are aligned in the advancing and retracting directions. A contaminant transfer screen device characterized by this.

[0108] According to this contaminant transfer screen device, since the time in the retracting state is longer, the risk of hard contaminants flowing in hitting the movable screen member is reduced, and as a result, the risk of damage to the drive mechanism or the like that drives the movable screen member is reduced.

[0109] Note that the movable screen member may move upward in the retracting state to transfer the contaminants upward, and then move downward in the advancing state.

[0110] (Appendix 1-2) The movable screen member transfers the contaminants upward by moving upward in the advancing state, and then moves downward in the retracting state. A contaminant transfer screen device according to Appendix 1-1, characterized by this.

[0111] (Appendix 1-3) The fixed screen member is provided with a plurality of fixed step portions along the longitudinal direction. The movable screen member is provided with a plurality of movable stepped portions along the longitudinal direction, and the foreign matter caught by the movable stepped portion is moved upward to be transferred to the fixed stepped portion above the movable stepped portion. The foreign matter transfer screen device according to appended claim 1-1 or 1-2, characterized in that.

[0112] (Appended claim 1-4) The movable screen member is provided with a home position for stopping the circulation operation in the retracted state. The foreign matter transfer screen device according to any one of appended claims 1-1 to 1-3, characterized in that.

[0113] Note that the movable screen member may once stop the circulation operation in the retracted state, and then resume the circulation operation and continue the circulation operation to return to the retracted state through the advanced state.

[0114] The movable screen member may repeatedly execute the circulation operation while the liquid is flowing in, and stop at the home position after the inflow of the liquid ends. Also, the movable screen member may stop at the home position when the circulation operation is performed a predetermined number of times, or may stop at the home position when the circulation operation is performed for a predetermined time, or may stop at the home position when performing one circulation operation.

[0115] In other words, the movable screen member continues the circulation operation in the advanced state except in the case of an emergency stop. Also, the movable screen member does not stop the circulation operation in the parallel state except in the case of an emergency stop. That is, the movable screen member may stop the circulation operation only when it is in the retracted state among the advanced state, the parallel state, and the retracted state.

[0116] The movable screen member stops at the home position in the retracted state, so that the time in the retracted state is longer than the time in the extended state, and the time in the retracted state is longer than the time in the parallel state.

[0117] (Appendix 1-5) The fixed screen member has higher rigidity than the movable screen member, and is characterized by the inclusion transfer screen device according to any one of Appendices 1-1 to 1-4.

[0118] Note that the movable screen member may be lighter than the fixed screen member. For example, the fixed screen member may be made of metal, and the movable screen member may be made of resin.

[0119] Even if the constituent elements are only included in each of the embodiments, modifications, and appendices described above, those constituent elements may be applied to other embodiments, other modifications, and appendices.

Explanation of Reference Numerals

[0120] 2 Screen unit for raw sludge 5 Water tank 6 Raw sludge inclusion transfer screen device 61 Fixed unit 611 Fixed screen member 6111 Fixed step portion 612 Fixed screen position regulating member 62 Movable unit 621 Movable screen member 621 Movable screen member 621N Normal movable screen member 621L Lightweight movable screen member 6211 Movable step portion 6212 Spacer for maintaining interval 622 Movable screen position regulating member 623 Movable frame 65 Driving mechanism 66 Control Unit W Predetermined Interval X, X1, X2, X3 Impurities 7 Scum Impurity Transfer Screen Device

Claims

1. In a foreign matter transfer screen device that cannot pass through the space connecting the upstream side and the downstream side and blocks the space on the upstream side, and transfers foreign matter contained in the liquid upward on the upstream side, a plurality of fixed screen members, a plurality of movable screen members that are arranged with a space between the adjacent fixed screen members and the space, and transfer the foreign matter upward by performing a circulating operation, the movable screen members are provided with a plurality of spacers for maintaining a space that are spaced apart in the longitudinal direction and project toward the adjacent fixed screen members, the spacer for maintaining the space is characterized in that the protruding end contacts the fixed screen member, and the protruding end slides with respect to the fixed screen member when the movable screen member performs the circulating operation.

2. the movable screen members are made of resin, the foreign matter transfer screen device according to claim 1, wherein the spacer for maintaining the space is formed of a resin having higher wear resistance than the resin of the movable screen member.

3. the fixed screen member has higher wear resistance than the spacer for maintaining the space, the foreign matter transfer screen device according to claim 1 or 2, wherein the spacer for maintaining the space is replaceable.

4. the foreign matter transfer screen device according to claim 1, wherein the movable screen member is lighter than the fixed screen member but has lower rigidity.

Images