Three-screw pump unit

Abstract

The invention provides a three-screw pump unit, and relates to the technical field of pumping, the three-screw pump unit comprises a three-screw pump, a motor, a magnetic coupling, a cover body and a liquid level detection structure, the three-screw pump and the motor are respectively arranged at two ends of the cover body, one end of a driving screw of the three-screw pump and a motor shaft of the motor respectively extend into the cover body, and the liquid level detection structure is arranged in the cover body. The magnetic coupler is located in the cover body, one end of the driving screw is in transmission connection with the motor shaft through the magnetic coupler, and the liquid level detection structure is arranged on the cover body and used for detecting whether liquid exists in the cover body or not. The three-screw pump is in transmission connection with the motor through the magnetic coupler, and the problems that in the prior art, due to the fact that dynamic sealing is abraded after running for a long time, sealing is not tight, and leakage is generated are solved; and in case of an accident, the leaked medium enters the cover body, and the liquid level detection structure can detect that the leaked medium exists in the cover body, so that a worker can be reminded in time to handle the leaked medium in time.

Description

Technical Field

[0001] This invention relates to the field of pumping technology, and more specifically, to a three-screw pump unit. Background Technology

[0002] In recent years, with the emergence of concepts such as "green shipping" and "green factories," people's awareness of environmental protection has been increasing. During the pumping process, leaks in the transported medium can have a significant impact on the environment; leaks of media such as marine fuel oil can not only pollute the marine environment but also lead to safety accidents. As society's environmental awareness grows, higher demands are being placed on "leak-free" pump technology.

[0003] Three-screw pump units, as important equipment for conveying fluid media, possess characteristics such as low pressure pulsation and stable operation due to their "three-screw" design, making them the "heart" of the entire pipeline system. They generally consist of a three-screw pump, coupling, support frame, and motor; the three-screw pump itself mainly comprises the driving and driven screws (the driving screw and two separately meshing driven screws), pump housing, bearings, and safety valve assembly.

[0004] Currently, the shaft seals of three-screw pumps mainly consist of skeleton oil seals and mechanical seals. Since three-screw pumps must be connected to a prime mover (motor) for operation, a coupling is required to connect the pump and the prime mover. With traditional couplings, the pump shaft end must be exposed; that is, one end of the drive screw of the three-screw pump must be exposed to provide a mounting position for the pump-end coupling. Therefore, traditional three-screw pumps must be equipped with shaft seals to prevent media leakage at the shaft end. Currently, shaft seals are mainly skeleton oil seals and mechanical seals, both of which are dynamic seals, and the risk of leakage is uncontrollable. Dynamic seals will wear down over time, leading to incomplete sealing and leakage. In addition, mechanical seals have high installation requirements; if the installation is incorrect, leakage may occur during operation.

[0005] In addition, existing three-screw pumps mainly use deep groove ball bearings, and the bearings are generally lubricated by the conveying medium or grease. When conveying low-viscosity media such as marine fuel oil, the poor lubricity of the medium causes ordinary deep groove ball bearings to wear after long-term use, which in turn affects the service life of the three-screw pump. Summary of the Invention

[0006] The present invention aims to solve at least one of the above-mentioned technical problems.

[0007] To address the aforementioned problems, this invention provides a three-screw pump unit, comprising a three-screw pump, a motor, a magnetic coupling, a housing, and a liquid level detection structure. The three-screw pump and the motor are respectively disposed at both ends of the housing. One end of the drive screw of the three-screw pump and the motor shaft of the motor extend into the housing. The magnetic coupling is located within the housing, and one end of the drive screw and the motor shaft are connected via the magnetic coupling. The liquid level detection structure is disposed on the housing and is used to detect the presence of liquid within the housing.

[0008] The three-screw pump unit provided by this invention has, but is not limited to, the following technical advantages compared to the prior art: The three-screw pump in this unit utilizes the contactless power transmission characteristic of magnetically driven pumps to connect with the motor. Specifically, the three-screw pump is connected to the motor via a magnetic coupling, enabling contactless power transmission during the operation of the motor-driven three-screw pump. This avoids the problems of wear and tear on dynamic seals during long-term operation, leading to poor sealing and leakage, which are common in traditional technologies. It also avoids the high installation requirements of mechanical seals in traditional technologies.

[0009] Specifically, one end of the drive screw in the three-screw pump is connected to the motor shaft via a magnetic coupling. Furthermore, a housing and a liquid level detection structure are installed between the three-screw pump and the motor. Because the magnetic coupling is located inside the housing, in case of unforeseen circumstances—such as damage to the magnetic coupling or design / installation defects—the pumped medium may still leak from the magnetic coupling. In this case, the leaked medium will enter the housing, preventing further leakage and environmental contamination. The liquid level detection structure will detect the leak within the housing, promptly alerting personnel for timely intervention.

[0010] Furthermore, the three-screw pump includes a pump housing assembly, and the magnetic coupling includes an electrical coupling, a pump coupling, an isolation cover, and a sealing structure. The pump coupling is connected to the driving screw, the isolation cover is fitted over the pump coupling, and the opening end of the isolation cover is connected to the corresponding end of the pump housing assembly through the sealing structure. The electrical coupling is sleeved outside the isolation cover and is connected to the motor shaft. There is no contact between the pump coupling and the isolation cover, and no contact between the electrical coupling and the isolation cover.

[0011] Furthermore, the three-screw pump unit also includes a speed detection sensor. The three-screw pump includes a pump housing assembly, and the speed detection sensor is disposed on the pump housing assembly. The speed detection sensor is used to detect the rotational speed of the driving screw or the driven screw of the three-screw pump.

[0012] Furthermore, the three-screw pump includes a pump housing assembly and a sliding bearing, the sliding bearing being disposed within the pump housing assembly, and the drive screw being assembled within the sliding bearing.

[0013] Furthermore, the pump housing assembly includes a pump housing body, a first end cap, and a bushing. The bushing is fixedly disposed inside the pump housing body. The first end cap is fixedly disposed at one end of the pump housing body near the cover. The sliding bearing is disposed at the inner circle of the first end cap. The drive screw is disposed inside the bushing and is assembled inside the sliding bearing.

[0014] Furthermore, the pump housing body is provided with a pump inlet and a pump outlet, the first end cap is used to restrict the sliding bearing from moving toward the cover, and the driving screw includes a main screw body and a main helical section and a balance drum disposed on the main screw body, the balance drum abutting against the end of the sliding bearing away from the cover; Wherein, along the axial direction of the driving screw, the pump outlet is closer to the balance drum than the pump inlet, and the diameter of the balance drum and the diameter of the main screw body conform to the following formula: ; in, The diameter of the balancing drum is... The diameter of the main screw body is given.

[0015] Furthermore, the sliding bearing has a first oil groove on one end face facing the balance drum. The first oil groove extends radially along the sliding bearing, with one end extending to the outer circle of the sliding bearing and the other end extending to the inner circle of the sliding bearing.

[0016] Furthermore, the active screw has a central oil return hole inside, which extends to both ends of the active screw.

[0017] Furthermore, the pump housing assembly also includes a second end cap and a driven screw that meshes with the driving screw. The second end cap is closed at one end of the pump housing body away from the first end cap, and one end of the driven screw abuts against the second end cap.

[0018] Furthermore, the second end cap includes a cap body, a limiting slider, and a fastener. The cap body is connected to the pump housing body. The limiting slider is installed on the inner end face of the cap body by the fastener. The limiting slider abuts against the corresponding driven screw. The end face of the limiting slider facing the driven screw is provided with a second oil groove. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the structure of a three-screw pump unit according to an embodiment of the present invention; Figure 2 This is a cross-sectional view of the three-screw pump unit according to an embodiment of the present invention; Figure 3 for Figure 2 A partial diagram showing the area after removing the motor and foot support; Figure 4 This is a schematic diagram of the active screw structure according to an embodiment of the present invention; Figure 5 This is a side view of the active screw structure according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of a sliding bearing according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of the second end cap from the inside view according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the limiting slider according to an embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures: 1. Three-screw pump; 11. Pump housing assembly; 111. Pump housing body; 1111. Pump inlet; 1112. Pump outlet; 112. Bushing; 113. First end cover; 114. Second end cover; 1141. Cover body; 1142. Limiting slider; 1143. Fastener; 1144. Second oil groove; 12. Driving screw; 121. Main screw body; 122. Balance drum; 123. Main helical section; 124. Central oil return hole; 13. Driven screw; 14. Sliding bearing; 141. First oil groove; 15. Safety valve assembly; 2. Motor; 21. Motor shaft; 3. Magnetic coupling; 31. Pump coupling; 32. Electrical coupling; 33. Isolation cover; 34. Sealing structure; 41. Liquid level detection structure; 42. Speed ​​detection sensor; 51. Cover; 52. Foot support. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings showing multiple embodiments according to this application. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort will fall within the scope of protection of this application.

[0022] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing specific embodiments only and is not intended to limit this application; the terms "comprising," "including," "having," "containing," etc., in the description, claims, and accompanying drawings of this application are open-ended terms. Therefore, "comprising," "including," or "having" refers to, for example, a method or apparatus having one or more steps or elements, but is not limited to having only these one or more elements. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0023] In the attached diagram, the X-axis represents the vertical direction, i.e., the front-to-back position, with the positive direction of the X-axis (where the arrow points) indicating forward and the negative direction (opposite to the positive direction) indicating backward. The Y-axis represents the horizontal direction, i.e., the left-to-right position, with the positive direction of the Y-axis (where the arrow points) indicating left and the negative direction (opposite to the positive direction) indicating right. The Z-axis represents the vertical direction, i.e., the up-to-down position, with the positive direction of the Z-axis (where the arrow points) indicating up and the negative direction (opposite to the positive direction) indicating down.

[0024] It should also be noted that the aforementioned X-axis, Y-axis and Z-axis are used only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0025] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0026] It should be emphasized that when the term "comprising / including" is used in this specification, it is used to explicitly indicate the presence of the stated feature, integer, step, or component, but does not exclude the presence or addition of one or more other features, integers, steps, parts, or groups of features, integers, steps, or parts.

[0027] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0028] See Figures 1-3 An embodiment of the present invention provides a three-screw pump unit, comprising a three-screw pump 1, a motor 2, a magnetic coupling 3, a housing 51, and a liquid level detection structure 41. The three-screw pump 1 and the motor 2 are respectively disposed at both ends of the housing 51. One end of the drive screw 12 of the three-screw pump 1 and the motor shaft 21 of the motor 2 extend into the housing 51. The magnetic coupling 3 is located inside the housing 51, and one end of the drive screw 12 and the motor shaft 21 are connected by transmission through the magnetic coupling 3. The liquid level detection structure 41 is disposed on the housing 51 and is used to detect whether there is liquid inside the housing 51.

[0029] It should be noted that the inventors of this application have discovered that in a magnetically driven pump, the magnetic coupling 3 is the core component for achieving contactless power transmission. Its function is to transmit the power of the motor 2 to the pump impeller while isolating the pump chamber from the outside world, thus achieving zero leakage in the pump. This is also the key difference between a magnetically driven pump and an ordinary mechanical seal pump.

[0030] Based on the characteristics of magnetically driven pumps, the inventors adapted them to a three-screw pump unit, ultimately producing unexpected technical effects. Specifically, in this embodiment, the three-screw pump 1 in the three-screw pump unit utilizes the contactless power transmission characteristic of magnetically driven pumps to connect with the motor 2. That is, the three-screw pump 1 is connected to the motor 2 via a magnetic coupling 3, achieving contactless power transmission during the operation of the motor 2 driving the three-screw pump 1. This avoids the problems of wear and tear, resulting in poor sealing and leakage caused by long-term operation of dynamic seals in traditional technologies. It is especially suitable for the main transportation of low-lubricity and leakage-sensitive media such as marine fuel oil and light diesel oil in the shipping industry (meeting the high requirements of "green shipping" for zero leakage); it also avoids the problem of high installation requirements of mechanical seals in traditional technologies.

[0031] Furthermore, one end of the drive screw 12 in the three-screw pump 1 is connected to the motor shaft 21 of the motor 2 via a magnetic coupling. In addition, a housing 51 and a liquid level detection structure 41 are provided between the three-screw pump 1 and the motor 2. Since the magnetic coupling 3 is located inside the housing 51, in case of an accident—that is, in the event of damage or failure of the magnetic coupling 3 or abnormal conditions such as design / installation defects—the pumped medium may still leak from the magnetic coupling 3. In this case, the leaked medium will enter the housing 51, preventing further leakage and environmental pollution. Furthermore, the liquid level detection structure 41 will detect the leaking medium inside the housing 51, promptly alerting personnel for timely handling.

[0032] Optionally, the liquid level detection structure 41 can be arranged at the bottom of the enclosure 51. In this way, if a leak occurs at the joint, even a small leak will be present at the bottom of the enclosure 51 and can be detected in time by the liquid level detection structure 41. The liquid level detection structure 41 can be a liquid level detection sensor, or more specifically, a liquid level detection sensor with an integrated alarm structure. When a leaking medium is detected inside the enclosure 51, it can issue an alarm in a timely manner; alternatively, the alarm structure can be placed in the work area where staff frequently stay.

[0033] Optionally, the three-screw pump unit also includes a foot support 52, which is located at the bottom of the housing 51 and is used to provide support for the installation of the entire three-screw pump unit. Furthermore, since the housing 51 is located between the three-screw pump 1 and the motor 2, the foot support 52 located at the housing 51 will also be balanced by forces in the front-back direction (X-axis direction, i.e., the front-back direction).

[0034] Since this three-screw pump unit does not use a traditional shaft seal for sealing, but instead uses a magnetic coupling 3 for transmission connection, and is particularly suitable for the shipbuilding industry, this three-screw pump unit can also be called a "shaft-seal-free magnetically driven marine three-screw pump unit".

[0035] See Figure 2-3 Optionally, the three-screw pump 1 includes a pump housing assembly 11, and the magnetic coupling 3 can be the same as existing magnetic couplings 3, including an electrical coupling 32, a pump coupling 31, an isolation cover 33, and a sealing structure 34. The pump coupling 31 is connected to the driving screw 12, the isolation cover 33 is placed over the pump coupling 31, and the opening end of the isolation cover 33 is connected to the corresponding end of the pump housing assembly 11 through the sealing structure 34. The electrical coupling 32 is sleeved outside the isolation cover 33 and is connected to the motor shaft 21; wherein, there is no contact between the pump coupling 31 and the isolation cover 33, and no contact between the electrical coupling 32 and the isolation cover 33.

[0036] In this embodiment, when the motor 2 is working, its motor shaft 21 drives the electric coupling 32 (outer magnetic rotor) to rotate. The magnetic field generated by the permanent magnet of the electric coupling 32 penetrates the isolation cover 33 and acts on the permanent magnet of the pump coupling 31 (inner magnetic rotor). The attraction of opposite magnetic fields drives the pump coupling 31 to rotate synchronously, thereby driving the drive screw 12 of the three-screw pump 1 to rotate, realizing the transportation of the medium. The entire power transmission process is without mechanical contact. After the isolation cover 33 is connected to the pump housing assembly 11 through the sealing structure 34, it completely blocks the channel between the pump chamber and the outside world, fundamentally eliminating the leakage risk of the mechanical seal pump. The sealing structure 34 can be an O-ring seal.

[0037] It should be noted that, under normal circumstances, the pumped medium will not leak from the front end of the drive screw 12 (the end that extends into the housing 51) after adopting the magnetic coupling 3. However, under abnormal operating conditions, component failure, or design / installation defects, medium leakage may still occur. The root causes of leakage mainly fall into three categories: damage to the isolation housing 33, failure of the sealing structure 34, and improper assembly / maintenance. Specific scenarios are as follows: I. Failure of core components: Damage to the isolation cover 33 (the main cause of leakage): The isolation cover is the main barrier to isolate the pump chamber from the outside world. Once it is damaged, the medium will overflow directly from the damaged point. Common damage scenarios include: hard particles (such as metal shavings and sand) mixed in the pump chamber, which impact or grind the inner wall of the isolation cover 33 as the active screw 12 and driven screw 13 rotate, resulting in thinning of the wall thickness and perforation after long-term operation.

[0038] The material of the isolation cover 33 is not compatible with the medium being transported: for example, using ordinary stainless steel isolation cover 33 to transport highly corrosive media (such as hydrochloric acid and strong alkali) will lead to corrosion and perforation; or the material has insufficient fatigue strength and cracks will appear under long-term alternating loads.

[0039] High-temperature aging: When transporting high-temperature media, if the heat resistance of the isolation cover material 33 is poor, it may soften, deform or even crack.

[0040] Overpressure rupture: The sudden closure of the pump outlet valve 1112 or pipeline blockage caused the pump chamber pressure to rise sharply, exceeding the pressure resistance limit of the isolation cover 33, resulting in rupture.

[0041] Design flaw: The wall thickness of the isolation cover 33 is insufficient and cannot withstand the pressure of actual working conditions.

[0042] II. The sealing structure 34 between the isolation cover 33 and the pump casing assembly 11 fails: The sealing structure 34 is aged, deformed, or the material is not resistant to media corrosion, resulting in loss of sealing performance.

[0043] III. Improper assembly, maintenance, or use

[0044] Installation deviation: The coaxiality error between motor 2 and three-screw pump 1 is too large, causing the electric coupling 32 and pump coupling 31 to be misaligned. Long-term operation causes wear on the isolation cover 33, which in turn damages the seal.

[0045] Maintenance oversight: Failure to periodically check the magnetism of the permanent magnets in the electrical connector 32 and pump connector 31 may lead to demagnetization or detachment of the magnets, resulting in unstable operation and accelerated wear of the isolation cover 33.

[0046] Irregular operation - no-load operation: When the pump is running dry, there is no medium cooling. The magnets of the isolation cover 33, the electric connection 32, and the pump connection 31 will heat up rapidly due to eddy current heating, causing the isolation cover 33 to soften and crack and the magnets to demagnetize.

[0047] The above lists the potential risks of media leakage due to the failure of the magnetic coupling. Based on this, as mentioned earlier, the three-screw pump unit also includes a housing 51 located between the three-screw pump 1 and the motor 2, as well as a liquid level detection structure 41. In the event of a leak from the magnetic coupling 3, the leaked medium will enter the housing 51, preventing further leakage and environmental contamination. Furthermore, the liquid level detection structure 41 will detect the leaking medium within the housing 51, promptly alerting personnel for timely handling.

[0048] See Figure 1-3 Optionally, the three-screw pump unit further includes a speed detection sensor 42. The three-screw pump 1 includes a pump housing assembly 11, and the speed detection sensor 42 is disposed on the pump housing assembly 11. The speed detection sensor 42 is used to detect the rotational speed of the driving screw 12 or the driven screw 13 of the three-screw pump 1.

[0049] It should be noted that when the magnetic coupling 3 experiences a decrease in demagnetization torque, the pump speed will decrease. If this situation is not detected in time, it will cause certain losses. Therefore, the pump speed can be detected by the speed detection sensor 42.

[0050] See Figure 2-3 Optionally, the pump housing assembly 11 includes a pump housing body 111, a first end cap 113, and a bushing 112. The bushing 112 is fixedly disposed inside the pump housing body 111. The first end cap 113 is fixedly disposed at one end of the pump housing body 111 near the cover 51. The sliding bearing 14 is disposed at the inner circle of the first end cap 113. The drive screw 12 is disposed inside the bushing 112 and is assembled inside the sliding bearing 14.

[0051] It should be noted that in the existing three-screw pump 1, the bearings supporting the rotation of the drive screw 12 are mainly deep groove ball bearings, and the lubrication of the bearings is generally provided by the conveying medium. When conveying low-viscosity media such as marine fuel oil, due to the poor lubricity of the medium, ordinary deep groove ball bearings will wear out after long-term use, which will affect the service life of the pump.

[0052] Therefore, in this embodiment, a sliding bearing 14 is used. The sliding bearing 14 is a bearing that operates under sliding friction. The sliding bearing 14 operates smoothly, reliably, and without noise. Under the condition of pumping medium lubrication, the driving screw 12 and the sliding bearing 14 are separated by the medium and do not come into direct contact. The medium between the driving screw 12 and the sliding bearing 14 forms an oil film, which can greatly reduce friction loss and surface wear. The oil film also has a certain vibration absorption capacity.

[0053] Furthermore, in this embodiment, similar to the existing three-screw pump 1, the pump housing assembly 11 includes a pump housing body 111, a first end cap 113, and a bushing 112. The first end cap 113 is installed at the front end of the pump housing body 111 and can also be called a front end cap. The bushing 112 constitutes the "circumferential sealing wall" of the medium cavity. And, as... Figure 2-3 As shown, the bushing 112 and the pump inlet 1111 form the low-pressure chamber of the pump; the inner circle of the front cover is used to install the sliding bearing 14 and to limit the sliding bearing 14 axially at least on one side.

[0054] Optionally, the sliding bearing 14 is made of ceramic material, and preferably, silicon carbide. The high hardness, low coefficient of friction, corrosion resistance, and high temperature resistance of silicon carbide effectively solve the problems of wear, impurities, and high temperature in the transportation of low-lubricating fuel oil for marine applications.

[0055] Among them, such as Figure 3 As shown, the speed detection sensor 42 can be specifically located at the first end cover 113 of the pump housing assembly 11, that is, at the front end cover, and the detection end of the sensor is not connected to the pump cavity. Since the speed detection sensor 42 is not in contact with the medium at this location, the detection accuracy and lifespan will be higher. However, this results in physical isolation between the speed detection sensor 42 and the drive screw 12. Based on this, the speed detection sensor 42 can be a magnetic induction sensor, and the surface of the drive screw 12 is embedded with a magnetic element for magnetic coupling with it.

[0056] See Figure 2-3Optionally, the pump housing body 111 is provided with a pump inlet 1111 and a pump outlet 1112, the first end cap 113 is used to restrict the sliding bearing 14 from moving toward the cover 51, and the driving screw 12 includes a main screw body 121 and a main helical section 123 and a balance drum 122 disposed on the main screw body 121, the balance drum 122 abutting against the end of the sliding bearing 14 away from the cover 51; In the axial direction of the driving screw 12, the pump outlet 1112 is closer to the balance drum 122 than the pump inlet 1111, and the diameter of the balance drum 122 and the diameter of the main screw body 121 conform to the following formula: ; in, The diameter of the balancing drum 122 is... The diameter is the diameter of the main screw body 121.

[0057] In this embodiment, the sliding bearing 14 is installed in the inner hole of the front end cover to limit the radial position of the drive screw 12. To limit the axial position of the drive screw 12, the first end cover 113 has a step that can axially limit the sliding bearing 14 to the front, i.e., prevent the sliding bearing 14 from moving forward. Furthermore, to limit the rearward movement of the drive screw 12, during pump operation, the drive screw 12 is subjected to the following forces: Figure 5 As shown.

[0058] like Figure 5 As shown, the active screw 12 is subjected to [something] when the pump is working. (Backwards) and The core reason for the two opposing forces (forward) is that "the inlet and outlet pressure difference (P) formed by the medium inside the pump acts on two different 'pressure-bearing surfaces' of the drive screw 12"—the high-pressure side medium generates a "thrust" on one pressure-bearing surface. The low-pressure side medium generates a reverse "thrust" on the other pressure-bearing surface. The two forces are in opposite directions, ultimately creating an axial force difference, which is an inevitable mechanical result of the screw pump's operation.

[0059] To ensure that the drive screw 12 does not move backward, it is necessary to Greater than According to Equation 3-96 of the "Screw Pump" manual, we obtain: ; ; Where P is the pressure difference between the inlet and outlet. The diameter of the balancing drum 122 is... The diameter of the main screw body 121. This is to ensure... Greater than Therefore, it is necessary to make and Satisfy the following formula: ; See Figure 3 and Figure 6 Optionally, the sliding bearing 14 is provided with a first oil groove 141 on one end face facing the balance drum 122. The first oil groove 141 extends radially along the sliding bearing 14, and one end of the first oil groove 141 extends to the outer circle of the sliding bearing 14, while the other end of the first oil groove 141 extends to the inner circle of the sliding bearing 14.

[0060] In this embodiment, a first oil groove 141 is provided on the rear end face of the sliding bearing 14. When the three-screw pump 1 is running, the balance drum 122 of the drive screw 12 rubs against the rear end face of the sliding bearing 14. The first oil groove 141 is used to store part of the medium, providing lubrication for the two contact end faces and reducing wear. In addition, the first oil groove 141 is also a channel for the medium to enter the interior of the sliding bearing 14 and form an oil film. When the three-screw pump 1 is running, part of the medium will leak into the first end cover 113 through the axial gap between the balance drum 122 of the drive screw 12 and the bushing 112, and then enter the sliding bearing 14 through the first oil groove 141 to form an oil film.

[0061] See Figure 4 Optionally, the active screw 12 is provided with a central oil return hole 124 inside, and the central oil return hole 124 extends through both ends of the active screw 12.

[0062] It is understood that when the three-screw pump 1 is running, some of the medium will leak into the first end cover 113 through the axial gap between the balance drum 122 and the bushing 112 of the drive screw 12, and then enter the sliding bearing 14 through the first oil groove 141 to form an oil film. In addition, the medium will continue to pass through the sliding bearing 14 into the isolation cover 33. If this part of the medium cannot be discharged, the cavity temperature of the isolation cover 33 will continue to rise, which will affect the service life of the isolation cover 33 and pose a risk of damage. Based on this, by opening a central oil return hole 124 in the drive screw 12, the medium in the cavity of the isolation cover 33 returns to the inlet end of the three-screw pump 11 through the central oil return hole 124 of the drive screw 12, forming a backflow, which can effectively suppress the rise in the medium temperature in the isolation cover 33.

[0063] See Figure 1-3Optionally, the pump housing assembly 11 further includes a second end cap 114 and a driven screw 13 that meshes with the driving screw 12. The second end cap 114 is closed on one end of the pump housing body 111 away from the first end cap 113, and one end of the driven screw 13 abuts against the second end cap 114.

[0064] In this embodiment, the second end cap 114 is installed at the rear end of the pump housing body 111, and can also be called the rear end cap, to limit the position of the driven screw 13.

[0065] Specifically, the meshing of the driven screw 13 and the driving screw 12 refers to the meshing of the main helical section 123 of the driving screw 12 with the helical section of the driven screw 13.

[0066] See Figure 7-8 Optionally, the second end cap 114 includes a cap body 1141, a limiting slider 1142, and a fastener 1143. The cap body 1141 is connected to the pump housing body 111. The limiting slider 1142 is installed on the inner end face of the cap body 1141 through the fastener 1143. The limiting slider 1142 abuts against the corresponding driven screw 13. The limiting slider 1142 has a second oil groove 1144 on one end face facing the driven screw 13.

[0067] In this embodiment, the limiting slider 1142 directly contacts the rear end face of the driven screw 13 to counteract the axial force on the driven screw 13. The end face of the limiting slider 1142 has a second oil groove 1144, such as a slotted groove, for storing media and reducing wear between the end of the driven screw 13 and the end face of the limiting slider 1142. Furthermore, the limiting slider 1142 is detachably connected to the cover body 1141 via fasteners 1143, such as screws, facilitating replacement after damage without requiring the replacement of the entire second end cover 114.

[0068] It should be noted that the conveying principle of the three-screw pump 1 is "to push the medium from the inlet to the outlet by forming a closed cavity through the meshing of three screws". This structure is inherently sensitive to "abnormal system pressure", and safety valve assembly 15 is commonly used to mitigate the risk. Based on this, if... Figure 3 As shown, the three-screw pump 1 also includes existing mounting valve assemblies.

[0069] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" and "second" may explicitly or implicitly include at least one of those features.

[0070] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A three-screw pump unit, characterized in that, The device includes a three-screw pump (1), a motor (2), a magnetic coupling (3), a housing (51), and a liquid level detection structure (41). The three-screw pump (1) and the motor (2) are respectively located at both ends of the housing (51). One end of the drive screw (12) of the three-screw pump (1) and the motor shaft (21) of the motor (2) extend into the housing (51). The magnetic coupling (3) is located inside the housing (51), and one end of the drive screw (12) and the motor shaft (21) are connected by transmission through the magnetic coupling (3). The liquid level detection structure (41) is located on the housing (51) and is used to detect whether there is liquid inside the housing (51).

2. The three-screw pump unit according to claim 1, characterized in that, The three-screw pump (1) includes a pump housing assembly (11), and the magnetic coupling (3) includes an electrical coupling (32), a pump coupling (31), an isolation cover (33), and a sealing structure (34). The pump coupling (31) is connected to the driving screw (12), the isolation cover (33) is placed over the pump coupling (31), and the opening end of the isolation cover (33) is connected to the corresponding end of the pump housing assembly (11) through the sealing structure (34). The electrical coupling (32) is sleeved on the outside of the isolation cover (33) and is connected to the motor shaft (21). There is no contact between the pump coupling (31) and the isolation cover (33), and no contact between the electrical coupling (32) and the isolation cover (33).

3. The three-screw pump unit according to claim 1, characterized in that, It also includes a speed detection sensor (42). The three-screw pump (1) includes a pump housing assembly (11). The speed detection sensor (42) is disposed on the pump housing assembly (11). The speed detection sensor (42) is used to detect the rotational speed of the driving screw (12) or the driven screw (13) of the three-screw pump (1).

4. The three-screw pump unit according to claim 1, characterized in that, The three-screw pump (1) includes a pump housing assembly (11) and a sliding bearing (14). The sliding bearing (14) is disposed inside the pump housing assembly (11), and the drive screw (12) is assembled inside the sliding bearing (14).

5. The three-screw pump unit according to claim 4, characterized in that, The pump housing assembly (11) includes a pump housing body (111), a first end cap (113), and a bushing (112). The bushing (112) is fixedly disposed inside the pump housing body (111). The first end cap (113) is fixedly disposed at one end of the pump housing body (111) near the cover (51). The sliding bearing (14) is disposed at the inner circle of the first end cap (113). The drive screw (12) is disposed inside the bushing (112).

6. The three-screw pump unit according to claim 5, characterized in that, The pump housing body (111) is provided with a pump inlet (1111) and a pump outlet (1112). The first end cap (113) is used to restrict the sliding bearing (14) from moving toward the cover (51). The driving screw (12) includes a main screw body (121) and a main helical section (123) and a balance drum (122) provided on the main screw body (121). The balance drum (122) abuts against the end of the sliding bearing (14) away from the cover (51). In the axial direction of the driving screw (12), the pump outlet (1112) is closer to the balance drum (122) than the pump inlet (1111), and the diameter of the balance drum (122) and the diameter of the main screw body (121) conform to the following formula: ； in, The diameter of the balancing drum (122) is... The diameter of the main screw body (121) is given.

7. The three-screw pump unit according to claim 6, characterized in that, The sliding bearing (14) has a first oil groove (141) on one end face facing the balance drum (122). The first oil groove (141) extends radially along the sliding bearing (14), with one end of the first oil groove (141) extending to the outer circle of the sliding bearing (14) and the other end of the first oil groove (141) extending to the inner circle of the sliding bearing (14).

8. The three-screw pump unit according to claim 6, characterized in that, The active screw (12) is provided with a central oil return hole (124) inside, which extends to both ends of the active screw (12).

9. The three-screw pump unit according to claim 5, characterized in that, The pump housing assembly (11) further includes a second end cap (114) and a driven screw (13) that meshes with the driving screw (12). The second end cap (114) is closed at one end of the pump housing body (111) away from the first end cap (113), and one end of the driven screw (13) abuts against the second end cap (114).

10. The three-screw pump unit according to claim 9, characterized in that, The second end cap (114) includes a cap body (1141), a limiting slider (1142), and a fastener (1143). The cap body (1141) is connected to the pump housing body (111). The limiting slider (1142) is installed on the inner end face of the cap body (1141) through the fastener (1143). The limiting slider (1142) abuts against the corresponding driven screw (13). The limiting slider (1142) has a second oil groove (1144) on one end face facing the driven screw (13).

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