JP7722938B2 - pump - Google Patents

Description

The present invention relates to a pump.

Patent Document 1 discloses a pump that has a bypass pipe connected to the pump casing, an on-off valve installed in the bypass pipe, and that opens the on-off valve during maintenance operations that do not involve drainage, allowing some of the pumped water to be returned through the bypass pipe and used to clean the area around the pump casing in the suction tank. Patent Document 2 discloses a pump that has an openable inspection window in the pump casing, allowing an endoscope to be inserted through this inspection window to inspect the inside of the pump casing.

Patent No. 5063744 Patent No. 6706163

The pump in Patent Document 1 gives no consideration to inspection of the inside of the pump casing. The pump in Patent Document 2 gives no consideration to cleaning the inside of the suction tank. In other words, neither Patent Document 1 nor Patent Document 2 gives any consideration to balancing maintenance and inspection of pump equipment, including the suction tank.

The objective of the present invention is to provide a pump that allows for both maintenance and inspection of pump equipment, including the suction tank.

The present invention provides a pump system comprising: a cylindrical pump casing partially disposed within a suction tank; an impeller rotatably disposed within the pump casing for discharging water from the suction tank; a bypass pipe disposed outside the pump casing, branched off and connected downstream of the impeller, and returning a portion of the pumped water discharged through the pump casing to the suction tank; and an on-off valve disposed within the bypass pipe, 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 comprising: a first pipe extending in a direction intersecting the pump casing; a first end branched off and connected to the first pipe; a second pipe having a second end disposed within the suction tank and for discharging returned water into the suction tank, wherein the on-off valve is a flap valve disposed within the first pipe between the first end of the second pipe and the pump casing and which 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, wherein an end of the first pipe opposite to the pump casing is closed by a door at least a portion of which is translucent and can be opened and closed, and the flap valve has a window through which the inside of the pump casing can be seen from the outside through the door .

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 the area around the pump casing to be cleaned (maintained). 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 located 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, this pump allows for both maintenance and inspection of the pump equipment, including the suction tank.

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 sealing structure can be reduced. Furthermore, the second pipe, with its second end located inside the suction tank, prevents the occurrence of air-sucking vortices that can occur inside the suction tank during normal operation.

This invention allows for both maintenance and inspection of pump equipment, including suction tanks.

1 is a cross-sectional view of a pump according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of part II in FIG. 1 . FIG. 3 is an enlarged cross-sectional view of part III in FIG. 2 . IV arrow view of FIG. 3. 5 is a view similar to FIG. 4 taken along the arrows and showing the door in an open state. FIG. 6 is a partial cross-sectional view taken along the arrow VI in FIG. 3 . FIG. 2 is a schematic diagram showing the configuration of a flap valve. Graph showing changes in pump performance.

The following describes an embodiment of the present invention with reference to the drawings.

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

The vertical pump 10 comprises a pump casing 12, a rotating shaft 15, an impeller 16, a motor 17, and a control unit 18. 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 pump 10, for example, when normal operation has not been performed for an extended period of time. The motor 17 (impeller 16) rotates at a slower speed (lower rotational speed) than during normal operation to minimize the discharge volume.

In the vertical pump 10 of this embodiment, a T-shaped bypass pipe 20 is branched off and connected to the pump casing 12 to return a portion of the pumped water to the suction tank 2 during maintenance operation to clean the inside of the suction tank 2. A flap valve (on-off valve) 32 is attached to the bypass pipe 20. In addition, an openable door 26 is provided on the bypass pipe 20 to enable inspection of the inside of the pump casing 12 using a measuring device such as an endoscope (not shown) when operation is stopped.

Specifically, referring to Figure 1, the pump casing 12 is inserted into a through-hole formed in the installation floor 1 and fixed to the installation floor 1. The pump casing 12 includes a lift pipe 13 disposed within the suction tank 2 and a discharge elbow 14 disposed on the installation floor 1. The lift pipe 13 extends vertically and includes suction ports 13a disposed at intervals on the bottom 3 of the suction tank 2. The discharge elbow 14 is a curved pipe with its axis bent at 90 degrees.

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

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

The motor 17 is a drive source mechanically connected to the upper end of the rotating 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 rotating shaft 15 at a predetermined rotation speed in response to commands from the control unit 18.

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

Continuing to refer to Figure 1, two bypass pipes 20 are provided at opposing positions outside the lift 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.

Referring to Figure 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. It is a straight pipe extending perpendicular to the axis A of the pumping pipe 13 (see Figure 1). The interior of the horizontal pipe 21 and the interior of the pump casing 12 are spatially connected, allowing a portion of the pumped water in the pump casing 12 to flow into the horizontal pipe 21. The inner diameter of the horizontal pipe 21 is smaller than the inner diameter of the pump casing 12 (e.g., by 30 to 40%). However, the extension direction of the horizontal pipe 21 does not have to be a strictly perpendicular direction in the 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. The horizontal pipe 21 may also be a curved pipe.

Referring to Figure 3, a cylindrical connection portion 21c that connects to the vertical pipe 22 protrudes downward from the horizontal pipe 21. A cylindrical portion 21d that protrudes upward is provided on the horizontal pipe 21 at a position opposite the connection portion 21c. The cylindrical portion 21d is covered by a transparent lid 24. This allows the interior of the vertical pipe 22 to be seen through the lid 24.

Referring to Figures 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. The configuration of these components will be described in detail later.

Referring to FIG. 1, the vertical pipe 22 is a straight pipe of the same diameter as the horizontal pipe 21 and extends along the lift pipe 13. The vertical pipe 22 has an upper end (first end) 22a connected to the connection portion 21c of the horizontal pipe 21, and a lower end (second end) 22b disposed within the suction tank 2. The vertical pipe 22 and 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.

An endless ring pipe 23 that surrounds the lift pipe 13 is connected to the lower ends 22b of the two vertical pipes 22. The ring pipe 23 is annular and centered on the axis A of the lift pipe 13, and is disposed between the suction port 13a and the impeller 16. The ring pipe 23 is provided with a plurality of nozzles 23a spaced apart circumferentially, which discharge water toward the bottom 3 of the suction tank 2. This allows the water discharged from the nozzles 23a to scrape up sludge on the bottom 3 of the suction tank 2 and be discharged together with the water inside the suction tank 2. Note that the vertical pipes 22 may not be provided with ring pipes 23, and instead 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.

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

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

The door 26 is disk-shaped with a diameter larger than the diameter of the opening 25a, and when closed, the gap between it and the end plate 25 is sealed by a sealing member (not shown). The door 26 is made of a transparent plate with translucency, allowing the inside of the horizontal pipe 21 to be seen from the outside through the opening 25a. Therefore, the open/closed state of the flap valve 32 can be easily confirmed through the 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 the door 26. However, as long as only the portion of the door 26 corresponding to the opening 25a is translucent, the other portions may be opaque and not translucent.

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 Figure 3, the hinge 27 is attached to a retaining portion 28. The hinge 27 abuts against the retaining portion 28, holding the door 26 in an open position (open position) so that it extends along the axis of the horizontal piping 21. This allows the door 26 to be used as a support 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.

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

Referring to FIG. 6 , the flap valve 32 is rotatable integrally with the shaft 33, which is disposed in the bearing 21g and insertion hole 21h of the horizontal pipe 21. The bearing 21g and insertion hole 21h are located closer to the inner end 21a of the horizontal pipe 21 than the connecting portion 21c. The bearing 21g is a recessed portion recessed from the inside to the outside, and a ball bearing 34 is mounted therein to rotatably support the shaft 33. The shaft 33 is inserted into the insertion hole 21h , and a shaft seal 35 is mounted between the shaft 33 and the bearing 21g to prevent water leakage. Referring to FIG. 3 , the flap valve 32 is provided on the discharge elbow 14 side with a valve seat 21e having a through hole 21f that allows water to pass through. In this embodiment, the valve seat 21e is inclined outward (away from the discharge elbow 14) from top to bottom, but may extend perpendicular to the axis of the horizontal pipe 21.

Referring to Figure 1, the flap valve 32 opens and closes according to the difference between the pressure P inside the discharge elbow 14, the pressure Pd outside the flap valve 32 (external to the discharge elbow 14), and the pressure Ps inside the suction tank 2. During normal operation, the pressure P inside the discharge elbow 14 is lower than the pressure Pd outside the flap valve 32 and the pressure Ps inside the suction tank 2 (P < Pd ≦ Ps). This causes the flap valve 32 to rotate to the closed position shown by the solid line in Figure 3 and press against the outer surface of the valve seat 21e, blocking pumping from inside the discharge elbow 14 to the horizontal pipe 21 (closed state). During maintenance operation, the pressure P inside the discharge elbow 14 is higher than the pressure Pd outside the flap valve 32 and the pressure Ps inside the suction tank 2 (P > Pd ≧ Ps). As a result, the flap valve 32 rotates toward the open position shown by the dashed line in Figure 3 so as to move away from the valve seat 21e, allowing some of the pumped water in the discharge elbow 14 to flow in (open state). Here, the open state not only refers to the state in which the flap valve 32 is rotated to the open position shown by the dashed line in Figure 3, but also includes a state in which the flap valve 32 is separated from the valve seat 21e and allows the pumped water in the discharge elbow 14 to flow in.

Referring to Figures 3 and 6, the flap valve 32 comprises an opaque valve body 32a that does not transmit light, and a transparent window 32b that transmits light. The window 32b is located along the axis of the horizontal pipe 21, corresponding to the opening 25a, so that the inside of the discharge elbow 14 can be seen through the transparent door 26. This makes it easy to check the discharge status of pumped water through the door 26 and window 32b during normal operation.

Referring to Figure 6, the operating member 36 is attached to the outer end of the shaft 33 that protrudes from inside the horizontal pipe 21 to the outside, and is a rod that extends away from the shaft 33. When the flap valve 32 is in the closed position, the flap valve 32 can be rotated to the open position by manually operating the operating member 36 in a direction perpendicular to the plane of the paper in Figure 6, away from the plane of the paper. When the flap valve 32 is in the closed position, the flap valve 32 abuts against the valve seat 21e, so the operating member 36 cannot be operated in a direction perpendicular to the plane of the paper in Figure 6, towards the plane of the paper. 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 there is no need to operate the operating member 36.

The weight 37 is detachably attached to the tip of the operating member 36. Multiple types of weights 37 with different weights are available, and by replacing them with weights 37 of different weights, the weight (resistance) of the flap valve 32 can be changed, making it possible to adjust 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 (adjustment unit). However, the weight 37 may also be attached to the flap valve 32, as shown by the dashed dotted line in Figure 7. The adjustment unit attached to the flap valve 32 may also be multiple types of springs with different biasing forces. Alternatively, both weights 37 and springs may be used.

Referring to Figure 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.

Figure 8 is a graph showing changes in pump performance of the vertical pump 10 of this embodiment. In Figure 8, the horizontal axis is Q/Qopt, the ratio of flow rate Q to the optimal flow rate Qopt, and the vertical axis is H/Hopt, the ratio of head H to the optimal head Hopt. Depending on the specific speed, in Figure 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 operating region. In normal operation, the motor 17 is controlled to be in the rated operating region or the excessive flow rate region, and in managed operation, the motor 17 is controlled to be in the partial flow rate region.

In Figure 8, Qb1 and Qb2 are the results of adjusting the reflux amount by changing the weight of the 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 for Qb1 is greater than the flow rate for Qb2. In this way, the reflux amount can be adjusted to Qb1 or Qb2 by changing the weight of the 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 the weight 37, the same effect can be achieved by changing to a spring with a different biasing force.

Referring to Figure 8, when operating in the excessive flow rate range, the pump head H is lower than when operating in the partial flow rate range, and the pressure P in the discharge elbow 14 shown in Figure 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 closes, 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 has dropped due to drainage. However, in this embodiment, as shown in Figure 1, the vertical piping 22 of the bypass pipe 20, which is arranged around the lift pipe 13, 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. Note that during normal operation in the rated operating range, the discharge flow rate Q is lower than when operating in the excessive flow rate range, but stable drainage is possible.

When operating in the partial flow rate range, the pump head H is higher than when operating in the excessive flow rate range. Therefore, 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 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 allows a portion of the pumped water to be discharged near the suction port 13a via the bypass pipe 20, thereby scooping up sludge at the bottom 3 of the suction sump 2 and discharging it with 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, backflow occurs at the inlet (suction port 13a side) of the impeller 16, potentially causing 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. As a result, the vertical pump 10 of this embodiment can expand the range in which it can operate in the partial flow rate region during maintenance operation.

On the other hand, when inspecting the inside of the pump casing 12, the motor 17 is stopped to halt operation of the vertical pump 10. Then, as shown in Figures 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 device such as an endoscope is inserted into the pump casing 12 from the opening 25a through the through hole 21f. If the measuring device 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 for accurate inspection of the inside of the pump casing 12.

The vertical pump 10 configured in this manner has the following features:

The pump 10 includes a bypass pipe 20 that returns a portion of the pumped water to the suction tank 2, and a flap valve 32 that closes during normal operation and opens during maintenance operation. During maintenance operation, the flap valve 32 opens, allowing a portion of the pumped water to be discharged (returned) through the bypass pipe 20 into the suction tank 2, enabling 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 facing 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 inside of the pump casing 12. In this way, the pump 10 of this embodiment allows for both maintenance and inspection of the pump equipment, including the suction tank 2.

During normal operation, the flap valve 32 switches to a closed state, preventing the bypass pipe 20 from affecting the drainage through the pump casing 12, allowing the water in the suction tank 2 to be efficiently discharged. Furthermore, because no pumping pressure is applied to the door 26 during normal operation, the durability required for the door's 26 sealing structure can be reduced. Furthermore, the vertical pipe 22, with its lower end 22b located inside the suction tank 2, prevents the occurrence of air-sucking vortices that can occur in the suction tank 2 during normal operation.

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, thereby reducing the running costs of the pump equipment.

An operating member 36 that can open and close the flap valve 32 is provided on the shaft 33 of the flap valve 32, which protrudes from inside the horizontal pipe 21 to the outside. This improves workability when inserting a measuring instrument through the horizontal pipe 21 to inspect the inside of the pump casing 12.

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

The flap valve 32 is equipped with a weight 37 that can adjust the timing at which it switches from a closed state to an open state. This ensures that the flap valve 32 remains reliably closed during normal operation and can be reliably switched to an open state during maintenance operation.

A damping member 38 is provided to dampen the vibration of the flap valve 32 when it is opened and closed. This prevents chattering caused by the opening and closing of the flap valve 32.

The door 26 is provided with a holder 28 that holds it in an 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 when inserting a measuring instrument from the horizontal pipe 21 of the bypass pipe 20 into the pump casing 12, improving workability during inspection.

Note that the present invention is not limited to the configuration of the above embodiment, and various modifications are possible.

For example, the on-off valve may be a butterfly valve, etc., 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.

The pump may be of any type, provided it has a cylindrical pump casing, an impeller for discharging water, and is capable of switching between normal operation and controlled operation.

1 Installation floor 2 Suction tank 3 Bottom 10 Vertical pump (pump)
12 Pump casing 13 Lifting pipe 13a Suction port 14 Discharge elbow 15 Rotating shaft 16 Impeller 17 Motor 18 Control unit 20 Bypass pipe 21 Horizontal pipe (first pipe)
21a Inner end 21b Outer end (end)
21c Connection portion 21d Cylinder portion 21e Valve seat 21f Through hole 21g Bearing portion 21h Insertion portion 22 Vertical pipe (second pipe)
22a Upper end (first end)
22b Lower end (second end)
23 Annular piping 23a Nozzle 24 Lid 25 End plate 25a Opening 25b Bolt hole 26 Door 27 Hinge 28 Holding portion 29 Eyebolt 30 Bracket 32 Flap valve (on-off valve)
32a Valve body 32b Window 33 Shaft portion 34 Ball bearing 35 Shaft seal device 36 Operating member (operating portion)
37 Weight 38 Damping member (damping portion)
40 Support stand

Claims (5)

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 that 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 controlled operation;
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 returned water into the suction tank,
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 . 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 . 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. 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. 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.