pump

Abstract

To provide a pump that can realize both maintenance and inspection of a pump facility including a water suction tank.SOLUTION: A pump 10 comprises a pump casing 12, an impeller 16 rotatably arranged in the pump casing 12, a bypass pipe 20 branched and connected to a downstream side of the impeller 16 out of the pump casing 12, and an opening / closing valve 32 arranged in the bypass pipe 20. The bypass pipe 20 comprises a first pipe 21 extending in a direction intersecting with the pump casing 12, a second pipe 22 for discharging returned water into a water suction tank 2, and an openable / closable door 26 provided in the first pipe 21. The opening / closing valve 32 is arranged between a first end 22a of the second pipe 22 and the pump casing 12 out of the first pipe 21.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a pump. [Background technology]

[0002] Patent Document 1 discloses a pump in which a bypass pipe is connected to the pump casing and an on-off valve is provided in the bypass pipe, and the on-off valve is opened during maintenance operation that is not intended for drainage, allowing the area around the pump casing in the suction tank to be cleaned with a portion of the pumped water returned through the bypass pipe.Patent Document 2 discloses a pump in which an openable inspection window is provided in the pump casing and an endoscope can be inserted through this inspection window to inspect the inside of the pump casing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5063744 [Patent Document 2] Patent No. 6706163 Summary of the Invention [Problem to be solved by the invention]

[0004] The pump of Patent Document 1 gives no consideration to inspection of the inside of the pump casing. The pump of Patent Document 2 gives no consideration to cleaning of the inside of the suction sump. In other words, neither Patent Document 1 nor Patent Document 2 gives any consideration to compatibility between maintenance and inspection of pump equipment including the suction sump.

[0005] An object of the present invention is to provide a pump that allows for both maintenance and inspection of pump equipment including a suction tank. [Means for solving the problem]

[0006] The present invention provides a pump system comprising: a cylindrical pump casing, a portion of which is disposed within a suction tank; an impeller, which is rotatably disposed within the pump casing, for discharging water from the suction tank; a bypass pipe, which is disposed outside the pump casing, branched off and connected downstream of the impeller, for returning a portion of the pumped water discharged through the pump casing to the suction tank; and an on-off valve, which is disposed within the bypass pipe, and which switches to a closed state to block the return flow during normal operation and switches to an open state to allow the return flow during maintenance operation. The bypass pipe comprises a first pipe extending in a direction intersecting the pump casing, and a second pipe having a first end branched off and connected to the first pipe and a second end disposed within the suction tank, for discharging the returned water into the suction tank. The on-off valve is Inside between the first end of the second pipe and the pump casing. a flap valve that rotates in a direction away from the pump casing when the closed state is switched to the open state due to a pressure difference between the inside and outside of the pump casing, and an end of the first pipe opposite the pump casing is closed by a door having at least a portion that is translucent so as to be able to open and close, and the flap valve has a window through which the inside of the pump casing can be seen from the outside through the door. , provides a pump.

[0007] The pump is equipped with a bypass pipe that returns a portion of the pumped water to the suction tank, and an on-off valve that switches to a closed state during normal operation and to an open state during maintenance operation. Because the on-off valve switches to an open state during maintenance operation, a portion of the pumped water is returned (discharged) into the suction tank through the bypass pipe, allowing cleaning (maintenance) of the area around the pump casing. The bypass pipe is equipped with a first pipe that has an openable door at the end facing the pump casing, and the on-off valve is disposed between the first end of the second pipe of the first pipe and the pump casing. By opening the door and opening the on-off valve, a measuring device such as an endoscope can be inserted to inspect the inside of the pump casing. In this way, the pump of this aspect allows for both maintenance and inspection of the pump equipment, including the suction tank.

[0008] During normal operation, the on-off valve switches to a closed state, preventing the bypass pipe from affecting the drainage through the pump casing, allowing the water in the suction tank to be efficiently discharged. Furthermore, because no pumping pressure is applied to the door during normal operation, the durability required for the door's seal structure can be reduced. Furthermore, the second pipe with its second end located inside the suction tank can prevent the occurrence of air-sucking vortices that can occur inside the suction tank during normal operation. [Effects of the Invention]

[0009] The present invention makes it possible to perform both maintenance and inspection of pump equipment including a suction tank. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a pump according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of part II in FIG. [Figure 3] FIG. 3 is an enlarged cross-sectional view of part III in FIG. 2 . [Figure 4] IV arrow view of Figure 3. [Figure 5] 5 is a view similar to FIG. 4 taken in the direction of the arrow, showing the door in an open state. [Figure 6] FIG. 6 is a partial cross-sectional view taken along the arrow VI in FIG. 3 . [Figure 7] FIG. 2 is a schematic diagram showing the configuration of a flap valve. [Figure 8] Graph showing changes in pump performance. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] Referring to FIG. 1, a vertical shaft pump (pump) 10 according to an embodiment of the present invention is attached to an installation floor 1 of a drainage pumping station, and discharges rainwater and the like that has flowed into a suction tank 2 located below the installation floor 1 downstream.

[0013] The vertical shaft pump 10 comprises a pump casing 12, a rotating shaft 15, an impeller 16, a motor 17, and a control unit 18, and the control unit 18 can perform normal operation for the purpose of draining water and controlled operation (minimum flow) for the purpose of not draining water. Controlled operation is performed for the purpose of maintaining the performance of the vertical shaft pump 10 when normal operation has not been performed for a long period of time, and the motor 17 (impeller 16) is rotated at a slower speed (lower rotational speed) than during normal operation to minimize the discharge volume.

[0014] In the vertical pump 10 of this embodiment, a T-shaped bypass pipe 20 is branched and connected to the pump casing 12 in order to return a portion of the pumped water to the suction sump 2 during maintenance operation to clean the inside of the suction sump 2, and a flap valve (on-off valve) 32 is attached to the bypass pipe 20. In addition, an openable door 26 is provided to the bypass pipe 20 so that the inside of the pump casing 12 can be inspected with a measuring device such as an endoscope (not shown) when operation is stopped.

[0015] Specifically, referring to Fig. 1, pump casing 12 is inserted into a through-hole formed in installation floor 1 and fixed to installation floor 1. Pump casing 12 includes a lifting pipe 13 disposed in suction tank 2 and a discharge elbow 14 disposed on installation floor 1. Lifting pipe 13 extends in the vertical direction and includes suction ports 13a disposed at intervals on bottom 3 of suction tank 2. Discharge elbow 14 is a bent pipe whose axis is bent at 90 degrees.

[0016] The rotating shaft 15 passes through the discharge elbow 14 and is disposed along the axis A of the riser pipe 13. The rotating shaft 15 is rotatably supported by a bearing disposed inside the riser pipe 13.

[0017] The impeller 16 is attached to the lower end of the rotating shaft 15 so as to be located at the bottom inside the lifting pipe 13. The impeller 16 rotates integrally with the rotating shaft 15 and discharges water from the suction tank 2 through the inside of the pump casing 12.

[0018] The motor 17 is a drive source mechanically connected to the upper end of the rotary shaft 15 located outside the pump casing 12. The motor 17 is electrically connected to the control unit 18, and rotates the impeller 16 via the rotary shaft 15 at a predetermined rotation speed in response to a command from the control unit 18.

[0019] Control unit 18 is configured with a personal computer. However, control unit 18 may also be configured with a single or multiple microcomputers and other electronic devices. Control unit 18 determines whether to perform normal operation, maintenance operation, or shutdown based on the water level in suction tank 2, and controls motor 17 so that rotating shaft 15 rotates at a rotation speed determined according to the operation to be performed. The water level in suction tank 2 is detected by, for example, a water level sensor disposed in suction tank 2. Control unit 18 stops rotation of motor 17 when shutdown is required, rotates motor 17 at a constant speed to minimize discharge volume when maintenance operation is required, and rotates motor 17 at a constant speed higher than that when normal operation is required.

[0020] Continuing to refer to Figure 1, two bypass pipes 20 are provided at opposing positions outside the rise pipe 13. However, the number of bypass pipes 20 may be one, or three or more. Each bypass pipe 20 includes a horizontal pipe (first pipe) 21 branching off from the discharge elbow 14 downstream of the impeller 16, and a vertical pipe (second pipe) 22 branching off from the horizontal pipe 21.

[0021] 2, the horizontal pipe 21 has an inner end 21a connected to the discharge elbow 14 and an outer end (end) 21b remote from the discharge elbow 14, and is a straight pipe extending in a direction perpendicular to the axis A of the pumping pipe 13 (see FIG. 1). The interior of the horizontal pipe 21 and the interior of the pump casing 12 are spatially connected, and a portion of the pumped water in the pump casing 12 can flow into the horizontal pipe 21. The inner diameter of the horizontal pipe 21 is smaller (e.g., 30 to 40%) than the inner diameter of the pump casing 12. However, the extension direction of the horizontal pipe 21 does not have to be a perpendicular direction in the strict geometric sense, as long as the interior of the pump casing 12 can be seen through the opening of the inner end 21a when viewed from the opening of the outer end 21b. Furthermore, the horizontal pipe 21 may be a curved pipe.

[0022] 3, horizontal pipe 21 has a cylindrical connection portion 21c that protrudes downward and connects to vertical pipe 22. Horizontal pipe 21 has a cylindrical portion 21d that protrudes upward at a position opposite connection portion 21c. Cylindrical portion 21d is covered with a transparent lid 24. This allows the interior of vertical pipe 22 to be seen through lid 24.

[0023] 3 and 6, the horizontal pipe 21 is provided with a valve seat 21e, a bearing portion 21g, and an insertion hole 21h for mounting the flap valve 32. These components will be described in detail later.

[0024] Referring to FIG. 1 , the vertical pipe 22 is a straight pipe having the same diameter as the horizontal pipe 21, and extends along the lifting pipe 13. The vertical pipe 22 has an upper end (first end) 22a connected to the connecting portion 21c of the horizontal pipe 21, and a lower end (second end) 22b disposed within the suction tank 2. The interior of the vertical pipe 22 and the interior of the horizontal pipe 21 are spatially connected, and water that flows into the horizontal pipe 21 is discharged into the suction tank 2. However, the vertical pipe 22 may be a curved pipe as long as it can discharge water to the bottom 3 of the suction tank 2. Furthermore, the diameter of the vertical pipe 22 may be different from the diameter of the horizontal pipe 21 as long as it can discharge water into the suction tank 2.

[0025] An endless ring-shaped pipe 23 surrounding the rise pipe 13 is connected to the lower ends 22b of the two vertical pipes 22. The ring-shaped pipe 23 is annular about the axis A of the rise pipe 13, and is disposed between the suction port 13a and the impeller 16. A plurality of nozzles 23a that discharge water toward the bottom 3 of the suction tank 2 are provided at intervals in the circumferential direction on the ring-shaped pipe 23. This allows the water discharged from the nozzles 23a to scrape up sludge on the bottom 3 of the suction tank 2 and to be discharged together with the water in the suction tank 2. Note that the vertical pipes 22 may not be provided with ring-shaped pipes 23, and the nozzles 23a may be provided at the lower ends 22b of the vertical pipes 22, or the lower ends 22b of the vertical pipes 22 may be open inside the suction tank 2.

[0026] Referring to FIG. 3, the door 26 is rotatably attached via a hinge 27 to an end plate 25 attached to the outer end 21 b of the horizontal pipe 21 .

[0027] 3 to 5, end plate 25 is a metal ring having an opening 25a. End plate 25 is attached liquid-tight to outer end 21b of horizontal pipe 21, and opening 25a is formed so that its center coincides with the axis of horizontal pipe 21. End plate 25 is provided with bolt holes (fastening holes) 25b that keep door 26 closed, and a retaining portion 28 that holds door 26 in the open state. Retaining portion 28 is made of a plate attached below opening 25a and extends along installation floor 1 (see FIG. 1).

[0028] Door 26 is a disk-shaped member with a diameter larger than the diameter of opening 25a, and when closed, the gap between door 26 and end plate 25 is sealed by a sealing member (not shown). Door 26 is made of a transparent plate with translucency, and the inside of horizontal piping 21 can be seen from the outside through opening 25a. Therefore, the open / closed state of flap valve 32 can be easily confirmed through door 26 during both normal operation and maintenance operation. Furthermore, during maintenance operation, the return state of a portion of the pumped water can be easily confirmed through door 26. However, as long as only the portion of door 26 corresponding to opening 25a is translucent, the other portions may be opaque and not translucent.

[0029] A hinge 27 is attached to the lower end of the door 26, and a pair of eyebolts (fastening members) 29 are attached circumferentially spaced apart on the upper side opposite the hinge 27. As shown most clearly in FIG. 3, the hinge 27 is attached to a holder 28. When the hinge 27 abuts against the holder 28, the door 26 is held in an open position (open position) so that it extends along the axis of the horizontal pipe 21. This allows the door 26 to be used as a support base for inserting a measuring instrument such as an endoscope during inspection inside the pump casing 12. The eyebolt 29 is attached to the door 26 via a bracket 30. The door 26 is maintained in the closed state by rotating the door 26 from the open position to the closed position and tightening the eyebolt 29 into the bolt hole 25b.

[0030] 3 and 6, the flap valve 32 is an on-off valve that can rotate around a shaft portion 33. The flap valve 32 is provided with a window 32b and an operating member (operating portion) 36. Referring to Fig. 6, a weight (adjusting portion) 37 is attached to the operating member 36, and referring to Fig. 7, the flap valve 32 is provided with a damping member (damping portion) 38.

[0031] 6, the flap valve 32 can rotate integrally with the shaft portion 33, and this shaft portion 33 is disposed in the bearing portion 21g and the insertion hole 21h of the horizontal pipe 21. The bearing portion 21g and the insertion hole 21h are provided on the horizontal pipe 21 closer to the inner end 21a than the connection portion 21c. The bearing portion 21g is a recessed portion recessed from the inside to the outside, and a ball bearing 34 that rotatably supports the shaft portion 33 is attached inside. 21h A shaft 33 is inserted through the flap valve 32, and a shaft seal device 35 is attached between the shaft 33 to prevent water leakage. Referring to Figure 3, a valve seat 21e having a through hole 21f that allows water to pass through is provided on the discharge elbow 14 side of the flap valve 32. In this embodiment, the valve seat 21e is inclined outward (away from the discharge elbow 14) from the top to the bottom, but it may also extend in a direction perpendicular to the axis of the horizontal piping 21.

[0032] Referring to FIG. 1, the flap valve 32 opens and closes according to the difference between the pressure P in the discharge elbow 14, the pressure Pd outside the flap valve 32 which is outside the discharge elbow 14, and the pressure Ps in the water suction tank 2. During normal operation, the pressure P in the discharge elbow 14 is less than the pressure Pd outside the flap valve 32 and the pressure Ps in the water suction tank 2 (P < Pd ≦ Ps). As a result, the flap valve 32 rotates to the closed position shown by the solid line in FIG. 3 and is pressed against the outer surface of the valve seat 21e, blocking the pumping water from flowing from the discharge elbow 14 into the lateral pipe 21 (closed state). During the control operation, the pressure P in the discharge elbow 14 is greater than the pressure Pd outside the flap valve 32 and the pressure Ps in the water suction tank 2 (P > Pd ≧ Ps). As a result, the flap valve 32 rotates to the open position side shown by the dashed line in FIG. 3 away from the valve seat 21e, allowing a part of the pumped water in the discharge elbow 14 to flow in (open state). Here, the open state includes not only the state of rotating to the open position shown by the dashed line in FIG. 3, but also the state where the flap valve 32 is separated from the valve seat 21e and the pumped water in the discharge elbow 14 can flow in.

[0033] Referring to FIGS. 3 and 6, the flap valve 32 includes an opaque valve body 32a without light transmittance and a transparent window 32b with light transmittance. The window 32b is provided at a position along the axis of the lateral pipe 21 corresponding to the opening 25a so that the inside of the discharge elbow 14 can be seen through the transparent door 26. Thereby, during normal operation, the discharge state of the pumped water can be easily confirmed through the door 26 and the window 32b.

[0034] Referring to FIG. 6, the operating member 36 is attached to the outer end of the shaft portion 33 protruding from the inside of the lateral pipe 21 to the outside, and is a rod extending in a direction away from the shaft portion 33. When the flap valve 32 is in the closed position, by manually operating the operating member 36 in the direction away from the paper surface among the directions perpendicular to the paper surface in FIG. 6, the flap valve 32 can be rotated to the open position side. When the flap valve 32 is in the closed position, since the flap valve 32 is in contact with the valve seat 21e, the operating member 36 cannot be operated in the direction approaching the paper surface among the directions perpendicular to the paper surface in FIG. 6. When the flap valve 32 is in the open position, the flap valve 32 rotates to the closed position due to its own weight and the weight of the operating member 36, so the operation of the operating member 36 is unnecessary.

[0035] The weight 37 is detachably attached to the tip of the operating member 36. A plurality of weights 37 are prepared, each with a different weight. By replacing the weight 37 with a different weight, the weight (resistance) of the flap valve 32 can be changed, and the timing at which the flap valve 32 switches from a closed state to an open state due to the pressure difference between the inside and outside of the discharge elbow 14 can be adjusted (adjustment unit). However, the weight 37 may also be attached to the flap valve 32, as shown by the dashed dotted line in FIG. 7. The adjustment unit attached to the flap valve 32 may also be a plurality of springs with different biasing forces. Alternatively, both the weight 37 and the spring may be used.

[0036] 7, the damping member 38 is attached to the valve seat 21e side of the flap valve 32, and damps the vibration and amplitude of the flap valve 32 as it opens and closes. The damping member 38 can be configured to provide Coulomb damping through dynamic friction resistance, to provide viscous damping through viscous resistance, or to be made of an elastic material. Any configuration can be used for the damping member 38 as long as it can damp the vibration of the flap valve 32 without interfering with the opening and closing of the flap valve 32.

[0037] FIG. 8 is a graph showing changes in pump performance of the vertical pump 10 of this embodiment. In FIG. 8, the horizontal axis represents the ratio Q / Qopt of the flow rate Q to the optimum flow rate Qopt, and the vertical axis represents the ratio H / Hopt of the head H to the optimum head Hopt. Although it depends on the specific speed, in FIG. 8, the region where Q / Qopt is less than approximately 70% is the partial flow rate region, the region where Q / Qopt is approximately 120% or more is the excessive flow rate region, and the range between these is the rated operation region. In normal operation, the motor 17 is controlled so that the pump is in the rated operation region or the excessive flow rate region, and in managed operation, the motor 17 is controlled so that the pump is in the partial flow rate region.

[0038] In Figure 8, Qb1 and Qb2 are the results of adjusting the reflux amount by changing the weight of weight 37. The weight 37 that produces the result Qb1 is lighter than the weight 37 that produces the result Qb2, and the flow rate of Qb1 is greater than the flow rate of Qb2. In this way, the reflux amount can be adjusted to Qb1 or Qb2 by changing the weight of weight 37, and the pump shut-off head H can be changed. In other words, by changing to a weight 37 with a different weight, the reflux start head Hb (timing) and the reflux amount Qb can be adjusted. Even if a spring is used instead of weight 37, a similar effect can be obtained by changing to a spring with a different biasing force.

[0039] Referring to FIG. 8, when the pump is operated in the excessive flow rate range, the pump head H is lower than when the pump is operated in the partial flow rate range. Therefore, the pressure P in the discharge elbow 14 shown in FIG. 1 is lower than the pressure Pd outside the flap valve 32 and the pressure Ps in the suction sump 2. As a result, the flap valve 32 is closed, and no pumped water is returned to the suction sump 2 through the bypass pipe 20. However, because the discharge flow rate Q increases, an air-sucking vortex may occur in the suction sump 2, where the water level drops due to drainage. However, in this embodiment, the vertical piping 22 of the bypass pipe 20, which is arranged around the lifting pipe 13 as shown in FIG. 1, can suppress the occurrence of an air-sucking vortex. Therefore, the vertical pump 10 of this embodiment is capable of draining water in the excessive flow rate range during normal operation. During normal operation in the rated operating range, the discharge flow rate Q is lower than when the pump is operated in the excessive flow rate range, but stable drainage is possible.

[0040] When operating in the partial flow rate range, the pump head H is higher than when operating in the excessive flow rate range, and the pressure P in the discharge elbow 14 shown in FIG. 1 is higher than the pressure Pd outside the flap valve 32 and the pressure Ps in the suction sump 2. As a result, when the pressure reaches or exceeds the return flow start head Hb, the flap valve 32 opens, and a portion of the pumped water is returned to the suction sump 2 through the bypass pipe 20. This causes a portion of the pumped water to be discharged near the suction port 13a through the bypass pipe 20, thereby scooping up sludge at the bottom 3 of the suction sump 2 and discharging it using the vertical pump 10. This allows the interior of the suction sump 2 to be cleaned. Furthermore, without return flow through the bypass pipe 20, a backflow occurs at the inlet (suction port 13a side) of the impeller 16, which can cause cavitation and vibration. However, in this embodiment, a portion of the pumped water is returned through the bypass pipe 20, thereby suppressing backflow at the impeller 16. Therefore, in the vertical pump 10 of this embodiment, the range in which it can operate in the partial flow rate region during the maintenance operation can be expanded.

[0041] On the other hand, when inspecting the inside of the pump casing 12, the motor 17 is stopped to stop operation of the vertical pump 10. Then, as shown in FIGS. 3 and 5, the eyebolt 29 is operated to open the door 26, and the operating member 36 is operated to manually open the flap valve 32. In this state, using the open flap valve 32 as a support, a measuring instrument such as an endoscope is inserted into the pump casing 12 from the opening 25a through the through hole 21f. If the measuring instrument is not stable during insertion, a support base 40 with a U-shaped cross section is placed on the door 26 as a special guiding jig. This allows the inside of the pump casing 12 to be inspected accurately.

[0042] The vertical pump 10 configured in this manner has the following features.

[0043] The pump 10 includes a bypass pipe 20 that returns a portion of the pumped water to the suction sump 2, and a flap valve 32 that closes during normal operation and opens during maintenance operation. Because the flap valve 32 opens during maintenance operation, a portion of the pumped water is discharged (returned) into the suction sump 2 through the bypass pipe 20, allowing cleaning (maintenance) of the area around the pump casing 12. The bypass pipe 20 includes a horizontal pipe 21 with an openable door 26 at its outer end 21b, which faces the pump casing 12. The flap valve 32 is located between the upper end 22a of the vertical pipe 22 of the horizontal pipe 21 and the pump casing 12. By opening the door 26 and setting the flap valve 32 to the open position, a measuring device such as an endoscope can be inserted to inspect the interior of the pump casing 12. Thus, the pump 10 of this embodiment allows for both maintenance and inspection of the pump equipment, including the suction sump 2.

[0044] During normal operation, flap valve 32 switches to a closed state, which prevents bypass pipe 20 from affecting the drainage that passes through pump casing 12, allowing water in sump 2 to be efficiently discharged. Furthermore, during normal operation, pumping pressure is not applied to door 26, which reduces the durability required for the seal structure of door 26. Moreover, vertical pipe 22 having lower end 22b that is located inside sump 2 can prevent the occurrence of an air-sucking vortex that can occur in sump 2 during normal operation.

[0045] The flap valve 32 opens and closes depending on the pressure difference between the inside and outside of the pump casing 12. Therefore, the flap valve 32 is closed during normal operation when the outside pressure is higher than the internal pressure of the pump casing 12, and is open during controlled operation when the outside pressure is lower than the internal pressure of the pump casing 12. In this way, no drive source is required to switch the flap valve 32 between the open and closed states, which reduces the running costs of the pump equipment.

[0046] An operating member 36 capable of opening and closing the flap valve 32 is provided on a shaft 33 of the flap valve 32 that protrudes from inside the horizontal pipe 21 to the outside. This improves the workability when inserting a measuring instrument from the horizontal pipe 21 to inspect the inside of the pump casing 12.

[0047] At least a portion of the door 26 is translucent, and the flap valve 32 has a window 32b that allows the interior of the pump casing 12 to be seen through the door 26. Therefore, during both normal operation and maintenance operation, the open / closed state of the flap valve 32 can be easily confirmed through the door 26. Furthermore, during normal operation, the discharge state of the pumped water can be easily confirmed through the door 26 and window 32b, and during maintenance operation, the return state of a portion of the pumped water can be easily confirmed through the door 26.

[0048] The flap valve 32 is provided with a weight 37 that can adjust the timing at which it switches from a closed state to an open state. This allows the flap valve 32 to be reliably maintained in a closed state during normal operation and to be reliably switched to an open state during maintenance operation.

[0049] The valve is provided with a damping member 38 that damps vibrations of the flap valve 32 caused by opening and closing, thereby preventing chattering caused by the opening and closing of the flap valve 32.

[0050] A holding portion 28 is provided to hold the door 26 in an open position so as to extend along the axis of the horizontal pipe 21. This allows the door 26 to be used as a support base when inserting a measuring instrument from the horizontal pipe 21 of the bypass pipe 20 into the pump casing 12, thereby improving workability during inspection.

[0051] The present invention is not limited to the configuration of the above embodiment, and various modifications are possible.

[0052] For example, the on-off valve may be a butterfly valve or the like, as long as it is configured to switch to a closed state that blocks reflux during normal operation and to switch to an open state that allows reflux during maintenance operation.

[0053] The pump may be of any type as long as it has a cylindrical pump casing and an impeller for discharging water, and is configured to be switchable between normal operation and controlled operation. [Explanation of symbols]

[0054] 1 Installation floor 2 Water absorption tank 3 bottom 10 Vertical pump (pump) 12 Pump casing 13. Lifting pipe 13a Intake port 14 Discharge elbow 15 Rotation axis 16 impeller 17 Motor 18 Control Unit 20 Bypass pipe 21 Side piping (1st piping) 21a Inner end 21b Outer end (end) 21c Connection 21d Cylinder part 21e Valve seat 21f through hole 21g bearing part 21h Insertion part 22 Vertical piping (second piping) 22a Upper end (1st end) 22b Lower end (2nd end) 23 Circular piping 23a Nozzle 24 Lid 25 End plate 25a opening 25b bolt hole 26 Door 27 Hinge 28 Holding part 29 Eyebolt 30 Bracket 32 Flap valve (on-off valve) 32a Valve body 32b Window 33 Shaft 34 Ball bearings 35 Shaft sealing device 36 Operating member (operating part) 37 Weight 38 Damping member (damping part) 40 Support stand

Claims

1. a cylindrical pump casing partially disposed within the suction tank; an impeller rotatably disposed within the pump casing for discharging water from the suction tank; a bypass pipe arranged outside the pump casing, branched off from the impeller downstream, for returning a portion of the pumped water discharged through the pump casing to the suction tank; an on-off valve that is disposed in the bypass pipe and switches to a closed state that blocks the return flow during normal operation and switches to an open state that allows the return flow during controlled operation; Equipped with The bypass pipe is a first pipe extending in a direction intersecting the pump casing; a second pipe having a first end branched and connected to the first pipe and a second end disposed within the suction tank, for discharging the returned water into the suction tank; Equipped with the on-off valve is a flap valve that is disposed in the first pipe between the first end of the second pipe and the pump casing, and that rotates in a direction away from the pump casing when switched from the closed state to the open state due to a pressure difference between the inside and outside of the pump casing, an end of the first pipe opposite to the pump casing is closed by a door having at least a portion thereof translucent so as to be openable and closable; The flap valve has a window through which the inside of the pump casing can be seen from the outside through the door.

2. The flap valve has a shaft portion that protrudes from the inside to the outside of the first pipe, The shaft portion is provided with an operating portion that can manually open and close the flap valve.

2. The pump of claim 1.

3. The pump according to claim 1 or 2, further comprising an adjustment unit that adjusts the timing at which the flap valve in the closed state switches to the open state.

4. The pump according to claim 1 , further comprising a damping section that damps vibration of the flap valve caused by opening and closing of the flap valve.

5. The pump according to claim 1 , further comprising a holding portion that holds the door in an open position so as to extend along an axis of the first pipe.

Images