Liquid-sealing pump device

Abstract

To prevent a backflow of fluid while suppressing cavitation.SOLUTION: A liquid-sealing pump includes: a casing having a columnar cavity formed therein; an impeller having a plurality of blades attached inside the casing in an eccentric manner; a port part for covering an end of the casing; and a check valve assembly provided communicating with the cavity and having a check valve for preventing an outflow of liquid from the cavity. Air is sucked and compressed by repeating expansion and compression of the air sealed in a space surrounded by the blades and an air-liquid interface of a liquid return flow generated by rotating the liquid sealed inside the casing by the impeller. An air suction port, an air discharge port, and a cavitation suppressing hole are formed in the port part. The cavitation suppressing hole communicates the cavity with the check valve assembly.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent Document 1 discloses a liquid ring pump including a housing containing a liquid and a rotor including a plurality of blades extending radially from a shaft and defining a conical space. In this liquid ring pump, a port member is disposed within the conical space and defines an inlet communicating with a low pressure region, a discharge port communicating with a high pressure region, and a cavitation suppression port communicating with a fluid source having a pressure between the low pressure region and the high pressure region. Also, each pair of adjacent blades cooperates with the liquid and the port member to surround a variable capacity bucket, and rotation of the rotor selectively positions the bucket in an inlet position adjacent to the inlet port for drawing in fluid, a cavitation suppression position in which the bucket is adjacent to the cavitation suppression port for allowing fluid to flow into the bucket, and a discharge position in which the bucket is adjacent to the discharge port for discharging fluid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2018-505343 Summary of the Invention [Problem to be solved by the invention]

[0004] In the invention described in Patent Document 1, there is a risk that liquid (sealing liquid) may flow back from the cavitation suppression port depending on the conditions. The reason for this will be explained below with reference to Figure 14. Figure 14 is a diagram showing an outline of a conventional liquid ring pump.

[0005] In the left half of Fig. 14, the volume of the buckets formed by adjacent rotor blades increases, and the pressure decreases (expansion side). In the right half of Fig. 14, the volume of the buckets decreases, and the pressure increases (compression side). Because the cavitation suppression port is formed on the compression side, when the intake pressure is close to atmospheric pressure, the pressure on the compression side becomes equal to or higher than atmospheric pressure, and there is a risk of backflow of fluid (gas and sealing liquid).

[0006] It is conceivable that the cavitation suppression port could be connected to the discharge port to make it easier for the sealing liquid to flow to the discharge port by gravity. However, even if the cavitation suppression port is connected to the discharge port, it is not possible to prevent all of the sealing liquid from flowing out, and there is a risk of backflow of fluid (especially gas).

[0007] Backflow from the cavitation suppression port can cause the following problems. For example, if the sealing liquid is water, leaking from the cavitation suppression port can cause the pump or peripheral equipment to leak, resulting in a risk of electric shock, or problems such as mold and corrosion due to moisture. If the sealing liquid is something other than water, such as an alkali, leaking from the cavitation suppression port can cause health hazards, such as chemical burns to workers who come into contact with the sealing liquid. For example, if gas leaks from the cavitation suppression port, and the gas is an irritant, toxic, or flammable gas, the gas leak can cause health hazards and endanger the safety of workers.

[0008] The present invention has been made in view of the above circumstances, and has an object to provide a liquid ring pump device that can prevent backflow of fluid while suppressing cavitation. [Means for solving the problem]

[0009] In order to solve the above problems, a liquid ring pump device according to the present invention includes, for example, a casing having a cylindrical cavity formed therein, an impeller provided eccentrically in the cavity with respect to the casing, the impeller having a plurality of blades, a port portion covering an end of the casing, and a check valve assembly provided in communication with the cavity, the check valve assembly having a check valve for preventing fluid from flowing out of the cavity, and is a liquid ring pump that sucks in and compresses gas by repeatedly expanding and compressing gas trapped in a space surrounded by the blades and a gas-liquid boundary surface of a liquid reflux generated by rotating a sealing liquid sealed inside the casing with the impeller, and is characterized in that an intake port, an exhaust port, and a cavitation suppression hole are formed in the port portion, and the cavitation suppression hole connects the cavity to the check valve assembly.

[0010] According to the liquid ring pump of the present invention, an intake port, an exhaust port, and a cavitation suppression hole are formed in a port portion covering an end of a casing, and the cavitation suppression hole communicates an internal cavity of the casing with a check valve assembly having a check valve, and the check valve prevents fluid from flowing out of the cavity. This makes it possible to prevent backflow of fluid while suppressing cavitation. The rotation axis of the impeller may be vertically above or below the central axis of the casing.

[0011] The check valve may be provided vertically above the liquid level of the sealing liquid when the impeller is not rotating. This allows maintenance such as replacement of the check valve to be performed without leakage of the sealing liquid, improving maintainability. Furthermore, by providing the check valve higher than the liquid level of the sealing liquid, the risk of continuous leakage of the sealing liquid can be minimized even if the check valve 53 is unable to function due to a malfunction or the like at an unexpected time.

[0012] The check valve assembly may further include an on-off valve provided in a flow path that communicates between the cavitation suppression hole and the check valve. This allows the check valve 53 to be replaced without draining the sealing water inside the cavity, regardless of the position of the check valve, while the piping is still connected to the liquid ring pump. In addition, by closing the on-off valve as necessary, gas can be taken in through the cavitation suppression hole only under operating conditions that cause cavitation. This prevents the disadvantages (reduced suction performance, increased power consumption, etc.) that would be caused by constantly taking in gas through the cavitation suppression hole.

[0013] The check valve assembly may include an electrically driven valve including the on-off valve, and the check valve assembly may have a control unit that opens and closes the on-off valve when the suction pressure reaches the cavitation generating pressure. This makes it possible to automatically take in gas through the cavitation suppression hole only under operating conditions under which cavitation occurs, and makes it possible to easily prevent disadvantages (such as reduced suction performance and increased power consumption) that are caused by constantly taking in gas through the cavitation suppression hole.

[0014] The check valve may be configured to be closed when the pressure in the cavity is close to atmospheric pressure, thereby preventing backflow when the liquid ring pump is started or stopped or when the pressure in the air chamber is close to atmospheric pressure.

[0015] The cavitation suppression hole or the check valve assembly may be provided with an orifice, which limits the amount of gas taken into the cavity through the cavitation suppression hole, thereby preventing an unnecessarily large amount of gas from being taken into the cavity.

[0016] When viewed along the rotation axis of the impeller, the cavitation suppression hole does not have to be completely blocked by the blades when the blades and the cavitation suppression hole overlap. If the cavitation suppression hole is configured to be completely blocked by the blades, there is a risk of abnormal noise being generated during operation of the liquid ring pump, but by ensuring that the cavitation suppression hole is not completely blocked by the blades, a detour is formed for the gas flow when the cavitation suppression hole and the blades overlap, and the generation of abnormal noise can be prevented. Effect of the Invention

[0017] According to the present invention, it is possible to prevent backflow of fluid while suppressing cavitation. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a side view that illustrates a schematic diagram of an example of a liquid ring pump device 1. [Diagram 2] 1A is a front view showing a schematic example of a liquid ring pump device 1, and FIG. 1B is a front view showing a schematic example of a liquid ring pump device 1 omitting the check valve assembly 50. FIG. [Diagram 3] FIG. 2 is a schematic diagram of a check valve assembly 50. [Figure 4] FIG. 2 is a diagram showing an outline of the pipe of an orifice 54. [Diagram 5] 1 is a schematic diagram showing the positional relationship between a casing 10, an impeller 20, and a port portion 30 in a liquid ring pump device 1. FIG. [Figure 6] FIG. 2 is a diagram showing an outline of a check valve assembly 50A. [Figure 7] 1 is a side view that diagrammatically illustrates an example of a liquid ring pump device 1A. [Figure 8] 1 is a side view showing a schematic diagram of an example of a liquid ring pump device 2. FIG. [Figure 9] FIG. 2 is a schematic diagram showing an outline of a check valve assembly 50C. [Figure 10] 1A and 1B are cross-sectional views showing an outline of the structure of a check valve 53A, in which (A) shows the open state and (B) shows the closed state. [Figure 11] FIG. 2 is a side view showing a schematic diagram of an example of a liquid ring pump device 3. [Figure 12] FIG. 2 is a front view showing a schematic diagram of an example of a liquid ring pump device 3. [Figure 13] 2 is a schematic diagram showing the positional relationship between a casing 10A, an impeller 20, and a port portion 30B in a liquid ring pump device 3. FIG. [Figure 14] FIG. 1 is a schematic diagram of a conventional liquid ring pump. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The liquid ring pump device of the present invention is a pump that operates by sealing a liquid (sealing liquid) inside a casing, rotating the casing with an impeller to create a liquid reflux, and repeating expansion and compression of the gas trapped in the space surrounded by the gas-liquid boundary surface of the liquid reflux, the impeller boss, and the blades, thereby creating a vacuum inside the casing.

[0020] <First embodiment> Fig. 1 is a side view showing a schematic example of a liquid ring pump device 1 according to a first embodiment of the present invention. Fig. 2(A) is a front view showing a schematic example of the liquid ring pump device 1, and Fig. 2(B) is a front view showing a schematic example of the liquid ring pump device 1 omitting a check valve assembly 50. In Fig. 1, essential parts are shown in cross section. The liquid ring pump device 1 mainly comprises a casing 10, an impeller 20, a port portion 30, a cover portion 40, and a check valve assembly 50.

[0021] The casing 10 has a cylindrical side surface 11 and a bottom surface 12 covering one end of the side surface 11, and has a cylindrical cavity 13 formed therein. An impeller 20 is provided in the cavity 13. Furthermore, the cavity 13 is filled with a liquid (sealing liquid) (not shown).

[0022] The impeller 20 has a plurality of blades 21, and is fixed to a main shaft (rotating shaft) 61 of a motor (not shown). A central axis ax1 of the impeller 20 coincides with the central axis of the main shaft 61, and the impeller 20 rotates in the direction of arrow R about the central axis ax1 as the main shaft 61 rotates. The central axis ax1 is provided at a position different from the central axis ax2 of the casing 10. In other words, the impeller 20 is provided eccentrically with respect to the casing 10. The central axis ax1 is located vertically above the central axis ax2.

[0023] The port portion 30 is a member that covers the end of the side surface 11 on which the bottom surface 12 is not provided, that is, the open end of the casing 10. The port portion 30 is mainly formed with a cavitation suppression hole 31, an intake port 32 (see FIG. 5), and an exhaust port 33 (see FIG. 5).

[0024] The cover portion 40 mainly has a cover body 41, a pump suction portion 42, and a pump discharge portion 43. The cover body 41 has a bottom surface 41a and a cylindrical side surface 41b, with an opening portion 41c provided to cover the port portion 30. A hole 41d is formed in the bottom surface 41a. The hole 41d and the cavitation suppression hole 31 communicate with each other via a cavity 41e inside the cover body 41.

[0025] Further, a supply liquid connection port 41f is formed on the bottom surface 41a to supply sealing liquid to the cavity 13. The supply liquid connection port 41f communicates with the cavity 13 via a cavity (not shown) inside the cover body 41. The sealing liquid supplied from the cavity 13 forms a liquid reflux and is then discharged from the pump discharge portion 43 together with the gas.

[0026] The pump suction section 42 and the pump discharge section 43 are provided in the cover body 41. The pump suction section 42 and the pump discharge section 43 are respectively connected to a pump suction port (not shown) and a pump discharge port (not shown) provided in the bottom surface 41a. The pump suction port and the pump discharge port are respectively connected to the intake port 32 and the exhaust port 33 via a cavity inside the cover body 41 (not shown).

[0027] However, the configuration of the cover portion 40 is not limited to this, and the cover portion 40 is not essential.

[0028] The check valve assembly 50 is provided in the cover body 41. The cavitation suppression hole 31, the hole 41d, and the cavity 41e connect the cavity 13 and the check valve assembly 50.

[0029] 3 is a diagram showing an outline of the check valve assembly 50. The check valve assembly 50 mainly includes a piping section 51, an on-off valve 52, a check valve 53, an orifice 54, and a strainer 55.

[0030] One end of the piping section 51 is provided to the cover section 40, and the other end is provided to the on-off valve 52. The piping section 51 has a nipple 51a and an elbow 51b. The piping section 51 communicates with the cavitation suppression hole 31, the on-off valve 52, and the check valve 53. Note that the form of the piping section 51 is not limited to this.

[0031] The on-off valve 52 is provided in a flow path that communicates between the cavitation suppression hole 31 and the check valve 53. The on-off valve 52 is an on-off valve that opens and closes the flow path, and in this embodiment, a ball valve that fully opens or fully closes the flow path is used. Note that the on-off valve 52 is not limited to a ball valve, and may be, for example, a gate valve. The on-off valve 52 may also be a valve that can adjust the opening degree of the flow path, such as a globe valve.

[0032] The check valve 53 is a valve that prevents the outflow of fluid from the cavity 13 (prevents backflow). The check valve 53 passes fluid only from the orifice 54 and strainer 55 side (upstream side, primary side) to the on-off valve 52 side (downstream side, secondary side), and does not allow fluid to flow from downstream to upstream. On the secondary side, the opening and closing of the check valve 53 depends on the pressure difference between the primary and secondary sides, and opens when the pressure on the primary side (here, atmospheric pressure) is higher, and closes when the pressure on the secondary side (here, the pressure in the cavitation suppression hole 31 that communicates with the piping section 51 and the on-off valve 52) is higher.

[0033] The check valve 53 is provided vertically above the liquid level of the sealing liquid when the impeller 20 is not rotating. For example, the cavity 13 is filled with sealing liquid in an amount that fills about half of the volume, and the liquid level is located near the height of the central axis ax2 (see FIGS. 1 and 2). Therefore, the direction of the flow path (axis ax3) is changed using the elbow 51b, and the check valve 53 is disposed vertically above the central axis ax2.

[0034] The orifice 54 has a pipe line with a throttle. FIG. 4 is a diagram showing an outline of the pipe line of the orifice 54. The pipe line has a circular pipe section 54a with a normal diameter and a throttle section 54b with an inner diameter smaller than that of the circular pipe section 54a. The orifice 54 adjusts the volume of the gas flowing into the check valve 53. The volume of the gas can be appropriately adjusted by appropriately setting the inner diameter of the throttle section 54b. In this embodiment, the orifice 54 is provided on the primary side of the check valve 53, but the orifice 54 may be provided on the secondary side of the check valve 53.

[0035] The strainer 55 has a mesh member and removes solid components from the gas flowing into the check valve 53. Note that the strainer 55 is not essential.

[0036] Fig. 5 is a schematic diagram showing the positional relationship between the casing 10, the impeller 20, and the port portion 30. Fig. 5 shows the casing 10, the impeller 20, and the port portion 30 as viewed from the front.

[0037] The impeller 20 has a thick-walled cylindrical impeller boss 22 and a plurality of blades 21 extending radially at equal intervals from the impeller boss 22. A main shaft 61 is provided in the impeller boss 22, and the impeller 20 rotates in the direction of arrow R (counterclockwise in FIG. 3) about a central axis ax1 as the main shaft 61 rotates. The impeller 20 is eccentric with respect to the casing 10.

[0038] The cavity 13 is filled with sealing liquid (e.g., water) L in an amount that fills approximately half the volume. When the impeller 20 rotates, the multiple blades 21 push out the sealing liquid L toward the outer periphery of the impeller 20, and the centrifugal force causes the sealing liquid L to circulate along the inner surface of the side surface 11, generating a reflux, and a space (air chamber G) is formed that is surrounded by the gas-liquid boundary surface S of the liquid reflux and the blades 21. Because the centers of the casing 10 and the impeller 20 are offset, the gas trapped in the air chamber G repeatedly expands and compresses during one rotation of the impeller 20.

[0039] The intake port 32 is disposed in region I where the volume of the air chamber G increases. In region I on the suction side, as the volume of the air chamber G increases, external gas is sucked in via the pump suction section 42 and the like. Moreover, the exhaust port 33 is disposed in region II where the air chamber G contracts. In region II, as the volume of the air chamber G decreases, the gas in the air chamber G is compressed and the gas is discharged to the outside via the pump discharge section 43 and the like.

[0040] When the liquid ring pump device 1 is operated under conditions where the pressure is lower than a certain condition in order to generate a vacuum in region I, air bubbles are generated in the sealing liquid L sealed in cavity 13, and these air bubbles are crushed during the compression process (air chamber G shrinks), causing cavitation, which not only generates noise and vibration, but also causes erosion in the base of the blades 21 of the impeller 20 and the side surface 11 of the casing 10. For this reason, cavitation suppression holes 31 are provided in region II, and gas is taken in from the outside through holes 41d and cavity 41e.

[0041] The diameter of the cavitation suppression holes 31 is larger than the thickness of the blades 21. Therefore, when viewed along the central axes ax1, ax2, the cavitation suppression holes 31 are not completely blocked by the blades 21 when the blades 21 and the cavitation suppression holes 31 overlap. If the diameter of the cavitation suppression holes 31 were smaller than the thickness of the blades 21, abnormal noises might occur when the cavitation suppression holes 31 are completely blocked by the blades 21. In contrast, by making the diameter of the cavitation suppression holes 31 larger than the thickness of the blades 21, a detour for the gas flow is formed when the cavitation suppression holes 31 and the blades 21 overlap, and the occurrence of abnormal noises can be prevented.

[0042] 1 and 3, a check valve assembly 50 is provided in communication with the cavitation suppression hole 31. When negative pressure occurs in the air chamber G during the compression process, the check valve 53 of the check valve assembly 50 takes in gas (here, air) from the outside via the strainer 55 and the orifice 54, thereby exerting a cavitation suppression effect. Furthermore, under conditions in which positive pressure occurs in the air chamber G and backflow occurs, the check valve 53 closes to prevent backflow of the sealing liquid and gas.

[0043] Furthermore, the check valve 53 is configured to be in a closed state when the pressure on the secondary side (cavitation suppression hole 31) is the same as the pressure on the primary side (atmospheric pressure). This makes it possible to prevent leakage of sealing liquid from the cavitation suppression hole 31 even when the liquid ring pumping device 1 is started and stopped. Therefore, by providing the check valve 53 in the flow path communicating with the cavitation suppression hole 31, cavitation can be suppressed under all operating conditions of the liquid ring pumping device 1 without requiring any additional operation and without the occurrence of backflow of sealing liquid and gas.

[0044] The check valve assembly 50 also has an on-off valve 52 that can be opened and closed depending on the conditions of use. Therefore, when the check valve 53 breaks down, the check valve 53 can be replaced without draining the sealing water inside the cavity 13 while the piping is still connected to the liquid ring pump device 1.

[0045] Also, by taking in the gas into cavity 13 through cavitation suppression holes 31, cavitation can be suppressed, but this causes a very slight decrease in suction performance and an increase in power (power consumption). Therefore, depending on the conditions of use, for example, under operating conditions in which cavitation does not occur, on-off valve 52 is closed to stop the intake of gas from check valve assembly 50, thereby preventing disadvantages that may occur from taking in gas into cavity 13 and enabling efficient operation.

[0046] Furthermore, because the check valve assembly 50 has the orifice 54, it is possible to limit the amount of gas taken into the cavity 13 from the cavitation suppression holes 31. When air is taken into the cavity 13 from the cavitation suppression holes 31, the power required to operate the liquid ring pumping device 1 tends to increase as the amount of air taken in increases. For this reason, by providing the orifice 54 and taking in air from the cavitation suppression holes 31 into the cavity 13 at an air volume appropriate to the characteristics of the liquid ring pumping device 1, the liquid ring pumping device 1 can be operated efficiently.

[0047] According to this embodiment, by connecting the cavity 13 to the check valve 53 of the check valve assembly 50 via the cavitation suppression hole 31, it is possible to prevent backflow of fluid while suppressing cavitation.

[0048] In addition, according to this embodiment, since the central axis ax1 is located vertically above the central axis ax2, the upper components such as the pump suction section 42 can be made smaller and the center of gravity of the liquid ring pump device 1 can be positioned low, thereby stabilizing the liquid ring pump device 1 during operation.

[0049] In this embodiment, the cavitation suppression holes 31 are round holes (the cross-sectional shape (hereinafter simply referred to as the cross-sectional shape) when cut at a plane perpendicular to the axis of the hole is round), but the shape of the cavitation suppression holes 31 is not limited to this. As long as the cavitation suppression holes 31 are not completely blocked by the blades 21 when they overlap, the cavitation suppression holes 31 may be of any shape. For example, the cross-sectional shape of the cavitation suppression holes 31 may be rectangular (square hole) or elliptical.

[0050] Furthermore, in this embodiment, the check valve assembly 50 has the on-off valve 52 between the piping section 51 and the check valve 53, but the position of the on-off valve 52 is not limited to this. The on-off valve 52 may be provided at any position as long as it is provided in the flow path that communicates between the cavitation suppression hole 31 and the check valve 53. For example, the on-off valve 52 may be provided between the nipple 51a and the elbow 51b, or between the hole 41d and the piping section 51.

[0051] Furthermore, the on-off valve 52 is not essential, and the check valve assembly 50 does not necessarily have to have the on-off valve 52. In this case, however, it is desirable to provide the check valve 53 vertically above the liquid level of the sealing liquid in the cavity 13 when the impeller 20 is not rotating. This allows maintenance such as replacement of the check valve 53 to be performed even if the on-off valve 52 is not provided, improving maintainability.

[0052] In the present embodiment, the check valve 53 is provided vertically above the liquid level of the sealing liquid when the impeller 20 is not rotating, but it is not essential to provide the check valve 53 vertically above the liquid level of the sealing liquid when the impeller 20 is not rotating. However, if the check valve 53 is lower (vertically below) than the liquid level of the sealing liquid, and the check valve 53 loses its function as a check valve due to the inclusion of dust, deterioration of the O-ring, corrosion, or the like, when, for example, the impeller 20 is rotated (pump operation) and then the rotation of the impeller 20 is stopped (pump stop), the sealing liquid rises inside the cavitation suppression hole 31 and the check valve assembly 50 to the liquid level of the sealing liquid, which may cause the sealing liquid to continue leaking from the check valve 53. By contrast, by making the check valve 53 higher than the liquid level of the sealing liquid, the risk of the sealing liquid continuing to leak from the check valve 53 when the check valve 53 is in a malfunctioning state can be minimized. Note that leakage of sealing liquid due to malfunction of the check valve 53 cannot be solved even if the on-off valve 52 is provided upstream of the check valve 53. Therefore, in order to reduce leakage of sealing liquid, it is desirable to provide the check valve 53 vertically above the liquid level of the sealing liquid when the impeller 20 is not rotating.

[0053] In addition, in this embodiment, the check valve assembly 50 has the orifice 54, but the orifice 54 is not essential. Even without the orifice 54, it is possible to prevent backflow of the fluid while suppressing cavitation.

[0054] 6 is a diagram showing an outline of a check valve assembly 50A that does not have an orifice 54. The check valve assembly 50A mainly has a piping section 51, an on-off valve 52, a check valve 53, a strainer 55, and a socket 56. The socket 56 is a pipe that connects the check valve 53 and the strainer 55. The liquid ring pump device 1 may be provided with a check valve assembly 50A that does not have an orifice, instead of the check valve assembly 50. Note that the strainer 55 and the socket 56 are not essential to the check valve assembly 50A.

[0055] Also, the liquid ring pump device 1 may include a check valve assembly 50A instead of the check valve assembly 50, and the orifice may be provided at a position other than the check valve assembly 50, for example, in the cavitation suppression hole. Fig. 7 is a diagram showing an outline of a liquid ring pump device 1A in which an orifice is provided in the cavitation suppression hole. Note that the check valve assembly 50A is not shown in Fig. 7.

[0056] The liquid ring pump device 1A mainly comprises a casing 10, an impeller 20, a port portion 30A, a cover portion 40, and a check valve assembly 50A. The port portion 30A mainly includes a cavitation suppression hole 31A, an intake port 32 (not shown in FIG. 7), and an exhaust port 33 (not shown in FIG. 7).

[0057] The cavitation suppression hole 31A has a circular pipe portion 31a and a throttle 31b whose inner diameter is smaller than that of the circular pipe portion 31a. The throttle 31b acts as an orifice and can adjust the amount of air flowing into the cavity 13 through the cavitation suppression hole 31A. The diameter of the circular pipe portion 31a is larger than the thickness of the blade 21, and the blade 21 will not completely block the cavitation suppression hole 31 even if the blade 21 and the cavitation suppression hole 31 overlap when viewed along the central axis ax1. The shape of the cavitation suppression hole 31A (circular pipe portion 31a and throttle 31b), like the cavitation suppression hole 31, is not limited to a round hole.

[0058] <Second embodiment> In the first embodiment of the present invention, the on-off valve 52 is a ball valve that is manually opened and closed, but the form of the on-off valve 52 is not limited to this. The liquid ring pump device 2 of the present invention will be described below. Note that the same parts as those in the first embodiment are given the same reference numerals and description thereof will be omitted.

[0059] 8 is a side view showing a schematic diagram of an example of a liquid ring pump device 2 according to a second embodiment of the present invention. The liquid ring pump device 2 mainly includes a casing 10, an impeller 20, a port portion 30, a cover portion 40, and a check valve assembly 50B.

[0060] The check valve assembly 50B mainly includes a piping section 51, a check valve 53, an orifice 54, a strainer 55, and an electrically driven valve 57.

[0061] The electrically driven valve 57 is an electrically driven valve that is driven by electricity, and is provided between the piping section 51 and the check valve 53. For example, the electrically driven valve 57 is a motor-operated valve having an on-off valve 52, an actuator 57a, and a control section 57b. Note that the on-off valve 52A may be a solenoid valve that operates the valve by the electromagnetic force of a solenoid.

[0062] The control unit 57b drives the actuator 57a to open the on-off valve 52 when a negative pressure at a level that is a condition for generating cavitation occurs on the suction side, and to close the on-off valve 52 in other cases. By opening the on-off valve 52, gas is taken into the cavity 13 via the check valve assembly 50B when operating under conditions under which cavitation occurs, and backflow of the sealing liquid and gas can be prevented when operating under conditions under which cavitation does not occur.

[0063] A temperature sensor (not shown) for measuring the temperature of the sealing liquid is provided in the make-up liquid supply pipe (not shown) communicating with the make-up liquid connection port 41f. A pressure sensor (not shown) for measuring the suction pressure is provided in the pump suction section 42 or the suction pipe (not shown) connected to the pump suction section 42. The control section 57b is connected to the temperature sensor and the pressure sensor. Based on the measurement results of the temperature sensor and the pressure sensor, the control section 57b opens and closes the on-off valve 52 when the suction pressure reaches a pressure at which cavitation occurs (hereinafter referred to as cavitation occurrence pressure). The suction pressure is the pressure in the pump suction section 42 or the suction pipe connected to the pump suction section 42.

[0064] The positions at which the temperature sensor and the pressure sensor are provided are not limited to those described above. For example, the pressure sensor may be provided in the piping section 51. Also, for example, the temperature sensor and the pressure sensor may be provided in the casing 10.

[0065] The cavitation generating pressure is approximately the same as the saturated vapor pressure of the sealing liquid, and varies depending on the type and temperature of the sealing liquid. For example, the on-off valve 52A has a memory unit, and information indicating the relationship between the type, temperature, and pressure of the sealing liquid and the saturated vapor pressure (hereinafter referred to as saturated vapor pressure information) is stored in the memory unit. The control unit 57b changes the cavitation generating pressure based on the saturated vapor pressure information, the type of the sealing liquid used, and the measured temperature of the sealing liquid.

[0066] When the suction pressure of the liquid ring pump device 2 (the pressure of the pump suction portion 42 or the suction piping connected to the pump suction portion 42) approaches the pressure of the external environment of the liquid ring pump device 1 (atmospheric pressure), the cavitation suppression hole 31 or the cavity 13 communicating with the cavitation suppression hole 31 becomes positive pressure, causing backflow from the cavitation suppression hole 31. Therefore, when the suction pressure is suddenly increased, there is a risk that the pressure sensor will not be able to detect the pressure and the control unit will not be able to open and close the motorized valve in time before the backflow starts.

[0067] Therefore, when the amount of change per time of the pressure measurement result by the pressure sensor is equal to or greater than a predetermined threshold value and the suction pressure is suddenly reduced, it is preferable that the control unit 57b opens the on-off valve 52 in advance when the pressure at the pump suction section 42 (intake port 32) reaches a predetermined threshold value I (the threshold value I is, for example, an arbitrary value in the vicinity of the cavitation generating pressure and is set to be the pressure immediately before the cavitation occurs) based on the measurement result of the pressure sensor, thereby preventing the occurrence of cavitation. Also, when the suction pressure is suddenly increased, it is preferable that the control unit 57b closes the on-off valve 52 in advance when the pressure at the pump suction section 42 (intake port 32) reaches a predetermined threshold value II (the threshold value II is, for example, an arbitrary value in the vicinity of the cavitation generating pressure and is set to be the pressure immediately before the cavitation occurs. Note that the threshold values ​​I and II are different values) based on the measurement result of the pressure sensor, thereby preventing backflow. In this way, the control unit 57b can control the on-off valve 52 to open and close the on-off valve 52 prior to starting and stopping the liquid ring pump device 1.

[0068] In addition, depending on the condition of the piping connected to the pump suction section 42, the pressure in the cavity 13 does not necessarily return to atmospheric pressure at the same time as the liquid ring pumping device 2 is stopped, and there is a risk of leakage of the sealing liquid depending on the fluid behavior. To prevent this, it is desirable for the control section 57b to close the on-off valve 52 before the liquid ring pumping device 2 is stopped.

[0069] According to this embodiment, because the electrically driven valve 57 automatically opens and closes the on-off valve 52, gas can be taken in through the cavitation suppression holes 31 only under operating conditions that cause cavitation. Therefore, the disadvantages of constantly taking in gas through the cavitation suppression holes 31 (such as reduced suction performance and increased power consumption) can be easily prevented.

[0070] In this embodiment, the control unit 57b controls the opening and closing of the on-off valve 52 based on the measurement results of the temperature sensor and the pressure sensor, but the method of controlling the opening and closing of the on-off valve 52 is not limited to this.

[0071] For example, the control unit 57b may control the opening and closing of the on-off valve 52 based on the power or current of the liquid ring pumping device 2. The power during operation of the liquid ring pumping device 2 is around 30 kPa, and the power decreases as the pressure changes toward the vacuum side and toward the atmospheric pressure side. Therefore, in the case of an operating condition in which the pressure changes only in the direction of the vacuum (for example, vacuuming from an atmospheric pressure state), when a change from an upward trend to a downward trend in the power or current value during operation of the liquid ring pumping device 2 is observed, that is, when the condition for cavitation to occur is met, the control unit 57b opens the on-off valve 52 and takes in gas from the cavitation suppression hole 31, thereby suppressing cavitation. In addition, under conditions in which the power or current value during operation of the liquid ring pumping device 2 is on the upward trend, that is, under conditions in which cavitation does not occur, the control unit 57b closes the on-off valve 52, thereby preventing backflow of the sealing liquid and gas.

[0072] Also, for example, the control unit 57b may control the opening and closing of the on-off valve 52 based on the operating time of the liquid ring pumping device 2. When the volume of the pressure-controlled target of the liquid ring pumping device 2 and the amount of gas inflow are fixed and the suction pressure over time can be predicted (for example, evacuation of a vacuum tank), cavitation can be suppressed by the control unit 57b opening the on-off valve 52 at a point in time when it is predicted from the operating time that the cavitation generation region will be entered and taking in gas from the cavitation suppression hole 31. Also, under conditions before the cavitation generation region is entered from the operating time, the control unit 57b closes the on-off valve 52, thereby preventing backflow of the sealing liquid and gas.

[0073] It is not essential that the check valve assembly 50 has the electrically driven valve 57, and the check valve may be provided with the function of the electrically driven valve 57. Figure 9 is a schematic diagram showing an outline of a check valve assembly 50C that does not have the electrically driven valve 57.

[0074] The check valve assembly 50C mainly includes a piping section 51, a check valve 53A, a strainer 55, and a socket 56.

[0075] The check valve 53A is set to open when the difference (differential pressure) between the pressure inside the cavity 13 and the outside pressure reaches a predetermined pressure. FIG. 10 is a cross-sectional view showing an outline of the structure of the check valve 53A, where (A) shows the open state and (B) shows the closed state. Note that hatching showing the cross section is omitted in FIG. 10. The check valve 53A mainly has a valve seat 53a, a valve body 53b, and an elastic member 53c. Note that in FIG. 10, the piping section 51 is connected to the right side of the page. The elastic member 53c is, for example, a coil spring, but is not limited to a coil spring.

[0076] The check valve 53A uses the elastic force of the elastic member 53c to open and close the flow path in response to the difference between the pressure inside the air chamber G adjacent to the cavitation suppression hole 31 and the cavitation suppression hole 31 (hereinafter simply referred to as the cavitation suppression hole 31) and the outside pressure. Under conditions where the pressure inside the cavitation suppression hole 31 is a positive pressure higher than the outside pressure, the elastic member 53c presses the valve body 53b against the valve seat 53a to close the check valve 53A, thereby preventing the backflow of the sealing liquid and gas (arrow F in FIG. 10).

[0077] When the pressure inside cavitation suppression hole 31 becomes a negative pressure lower than the outside pressure, the pressure difference pushes valve element 53b against the biasing force of elastic member 53c, causing valve element 53b to separate from valve seat 53a and opening check valve 53A. This allows gas (arrow O in Figure 10) to be taken in from the outside through strainer 55 and socket 56, thereby exerting a cavitation suppression effect.

[0078] In addition, by appropriately setting the elastic force of the elastic member 53c, the check valve 53A is closed when the pressure in the cavitation suppression hole 31 is close to atmospheric pressure. This prevents backflow even when the liquid ring pump is started or stopped or when the pressure in the air chamber G is close to atmospheric pressure, and gas can be taken into the cavity 13 only under operating conditions that require cavitation countermeasures. Therefore, cavitation can be suppressed without any operation by the operator under all operating conditions of the liquid ring pump. Furthermore, by appropriately setting the elastic force of the elastic member 53c in accordance with the suction pressure of the liquid ring pump device 2, the check valve 53A is opened by the negative pressure generated in the cavitation suppression hole 31 under operating conditions that cause cavitation, and external gas is taken in, thereby minimizing the disadvantages of taking in gas.

[0079] <Third embodiment> In the first embodiment of the present invention, the impeller 20 is eccentric with respect to the casing 10, and the central axis ax1 is located vertically above the central axis ax2, but the eccentric direction of the impeller 20 is not limited to this. The liquid ring pump device 3 of the present invention will be described below. Note that the same parts as those in the first embodiment are given the same reference numerals and description thereof will be omitted.

[0080] Fig. 11 is a side view showing an example of a liquid ring pump device 3 according to a third embodiment of the present invention. Fig. 12 is a front view showing an example of the liquid ring pump device 3. The liquid ring pump device 3 mainly includes a casing 10A, an impeller 20, a port portion 30B, a cover portion 40A, and a check valve assembly 50D.

[0081] The impeller 20 is provided eccentrically with respect to the casing 10. The central axis ax1 is located vertically lower than the central axis ax2. The casing 10A is identical to the casing 10 except for the position of a hole provided in the bottom surface 12A through which the main shaft 61 passes.

[0082] Port section 30B differs from port section 30 in the positions of cavitation suppression holes 31, intake ports 32, and exhaust ports 33, but is otherwise similar to port section 30. Figure 13 is a schematic diagram showing the positional relationship between casing 10A, impeller 20, and port section 30B.

[0083] Intake port 32 is located in region I where the volume of air chamber G increases, and exhaust port 33 is located in region II where air chamber G shrinks. Cavitation suppression holes 31 are provided in region II. Since central axis ax1 is located vertically below central axis ax2, cavitation suppression holes 31 are located vertically above central axis ax2.

[0084] 11 and 12. Cover part 40A mainly has a cover main body 41A, a pump suction part 42, and a pump discharge part 43. Cover main body 41A basically has a configuration in which the left and right sides of cover part 40 are inverted, but the positions of hole 41d and supply liquid connection port 41f are different from those of cover part 40.

[0085] The check valve assembly 50D mainly has a piping section 51A, an on-off valve 52, a check valve 53, an orifice 54, and a strainer 55. The piping section 51A is a nipple and differs from the piping section 51 in that it does not have an elbow.

[0086] The central axis ax1 is located vertically below the central axis ax2, and the cavitation suppression hole 31 is located vertically above the central axis ax2, i.e., above the liquid level of the sealing liquid when the impeller 20 is not rotating. Therefore, without using an elbow to make the axis ax3 vertical, the check valve 53 can be provided vertically above the liquid level of the sealing liquid when the impeller 20 is not rotating.

[0087] According to this embodiment, since the check valve assembly 50C is linear, the check valve assembly 50C can be made compact.

[0088] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope of the gist of the present invention. For example, in the liquid ring pump device of the present invention, the casing, the port portion, and the cover portion are arranged in this order, but the arrangement order of the casing, the port portion, and the cover portion is not limited to this.

[0089] In addition, "substantially" is a concept that includes not only the case of being strictly identical, but also an error or deformation to the extent that the identity is not lost. For example, "substantially orthogonal" is a concept that includes the case where it can be regarded as the same as orthogonal, for example, not limited to the case of being strictly orthogonal. In addition, for example, when expressing orthogonal, parallel, coincident, etc., it includes not only the case of being strictly orthogonal, parallel, coincident, etc., but also the case of approximately parallel, approximately orthogonal, approximately coincident, etc.

[0090] In addition, "vicinity" means including a certain range (which can be determined arbitrarily) near a reference position. For example, in the case of "near an end," it is a concept indicating a certain range of an area near the end, which may or may not include the end. [Explanation of symbols]

[0091] 1, 1A, 2, 3: Liquid ring pump device 10, 10A: Casing 11: Side 12: Bottom 13: Cavity 20: Impeller 21: Feather 22: Impeller boss 30, 30A, 30B: Port section 31, 31A: Cavitation suppression hole 31a: Circular tube part 31b :Aperture 32: Intake port 33: Exhaust port 40, 40A: Cover part 41, 41A: Cover body 41a: Bottom 41b: Side 41c: opening 41d: Hole 41e: hollow 41f: Refill fluid connection port 42: Pump suction section 43: Pump discharge section 50, 50A, 50B, 50C, 50D: Check valve assembly 51, 51A: Piping section 51a: Nipple 51b: Elbow 52: Opening and closing valve 53, 53A: Check valve 53a: Valve seat 53b: Valve body 53c: Elastic member 54: Orifice 54a: Circular tube part 54b :Aperture 55: Strainer 56 : Socket 57: Electrically operated valve 57a: Actuator 57b: Control section 61: Spindle

Claims

1. A casing having a cylindrical cavity formed therein; an impeller disposed in the cavity eccentrically with respect to the casing, the impeller having a plurality of blades; a port portion covering an end portion of the casing; a check valve assembly in communication with the cavity, the check valve assembly having a check valve for preventing fluid from exiting the cavity; a liquid ring pump that sucks in and compresses a gas by repeatedly expanding and compressing a gas trapped in a space surrounded by a gas-liquid boundary surface of a liquid reflux generated by rotating a sealing liquid sealed inside the casing with the impeller, The port portion is formed with an intake port, an exhaust port, and a cavitation suppression hole, The cavitation suppression hole communicates the cavity with the check valve assembly. A liquid ring pump device characterized by:

2. The check valve is provided vertically above the liquid level of the sealing liquid when the impeller is not rotating.

2. The liquid ring pump device according to claim 1 .

3. The check valve assembly further includes an on-off valve provided in a flow passage that communicates between the cavitation suppression hole and the check valve.

3. A liquid ring pump device according to claim 1 or 2.

4. the check valve assembly includes an electrically driven valve including the on-off valve, The check valve assembly has a control unit that opens and closes the on-off valve when the suction pressure reaches a cavitation generating pressure.

4. The liquid ring pump device according to claim 3.

5. The check valve is configured to be in a closed state when the pressure in the cavitation suppression hole is close to atmospheric pressure.

3. A liquid ring pump device according to claim 1 or 2.

6. The cavitation suppression hole or the check valve assembly is provided with an orifice.

6. A liquid ring pump device according to claim 1, wherein the liquid ring pump device is a pump unit.

7. When viewed along the rotation axis of the impeller, the cavitation suppression hole is not completely blocked by the blade when the blade and the cavitation suppression hole are overlapped.

7. A liquid ring pump device according to claim 1, wherein the liquid ring pump device is a pump unit.

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