A low-noise three-screw sewage oil pump with a mortise and tenon joint structure

Abstract

The present invention relates to a low-noise three-screw waste oil pump with a mortise and tenon joint structure. A driving screw and two driven screws are housed within a screw bushing. The screw bushing covers the spiral sections of the driving screw and the two driven screws, forming a spiral sealing chamber. The axial length of the screw bushing is greater than the spiral meshing portion formed by the driving screw and the driven screws, forming a screw bushing inlet cavity and a screw bushing inlet cavity. When liquid enters and exits the spiral sealing chamber, a buffer zone is formed with the pump inlet and outlet cavities, thereby reducing vibration and noise. The driving screw and the driven screw adopt a split structure and a mortise and tenon joint. The spiral sections and the axial force balancing portion are made of different materials, achieving low cost and high wear resistance. The present invention is very suitable for use in environments with limited space, low-noise transportation of gaseous and particulate media, rapid maintenance and replacement, and high requirements for overall size and weight. It has very important market economic value.

Description

Technical Field

[0001] The present invention relates to the technical field of three-screw pumps for conveying lubricating media, in particular to a three-screw waste oil pump for low-noise conveying of waste oil with lubricating properties in a state containing gas or granular solids of a certain size. Background Art

[0002] At present, it is very difficult for three-screw pumps to achieve low-noise transportation of dirty oil with lubricating properties in the state of gas or solid particles of a certain size. Some design structures can improve this situation, but the effect is not obvious.

[0003] Conventional designs utilize a single bar or forging as the blank for the driving and driven screws, with the helical section and axial force balancing section machined into different locations. Milling is often used to machine the helical section, with specialized grinding tools added for higher requirements for helical surface roughness. Because milling or grinding tools have a large turning radius, when the helical lead angle is large, they can remove a portion of the screw's axial force balancing section, reducing the sealing effectiveness and meshing smoothness of the combined axial force balancing sections of the driving and driven screws. This can negatively impact axial force balance and reduce vibration and noise.

[0004] Conventional designs often place a large distance between the spiral section and the axial force balancing section to prevent damage. However, this results in a longer screw, reduced rigidity, increased machining difficulty, and difficulty compressing the axial length of a three-screw pump. Therefore, a design with a mortise and tenon joint between the active and driven screws is required.

[0005] In order to facilitate the realization of gas-liquid-solid mixed transportation conditions, comprehensive considerations are taken from the overall structure: on the one hand, the screw spiral surface is designed as a non-sealed tooth shape. Although it reduces the conveying efficiency and discharge pressure, the spiral channel formed by the non-sealed tooth structure provides more convenience and redundancy for the passage of gas and solid particles of a certain size. The spiral channel provides pre-compression for the gas, controlling the vibration and noise of the pump group to a low value. The single-sided or double-sided side clearance of the non-sealed tooth shape leaves a certain buffer space for solid particles of a certain size to get stuck during the tooth bite process, reducing the probability of shaft seizure; on the other hand, the partition between the pump body and the screw bushing adopts an inclined structure, which is convenient for guiding the suction of the liquid in the inlet cavity and the discharge of the liquid flow in the outlet cavity. Combined with the larger volume advantage of the square pump body, it reduces the speed of the inlet and outlet flow channels, has better suction performance, and reduces vortex loss and liquid flow impact loss, making this type of design structure have great advantages in vibration noise, size and weight. Summary of the Invention

[0006] To prevent the axial force balancing portion of the active and passive screws from being damaged by milling cutters or grinders at larger lead helix angles, the present invention proposes a low-noise three-screw waste oil pump with a mortise and tenon joint structure. The helical section and axial force balancing portion of the active or passive screw are decomposed and designed into two sections, each of which is a single component with a mortise and tenon joint structure. These components are then machined separately and assembled using a mortise and tenon joint. The slender rod structure of the active and passive screws increases the rigidity of the individual components by shortening their axial length, which helps improve the accuracy of milling and grinding processes and reduce scrap rates. It also ensures that the axial force balancing portion is not damaged at any lead helix angle. Furthermore, the helical section and axial force balancing portion can be assembled using different materials, such as carbon steel for the axial force portion and alloy steel or other metals for the helical section, reducing costs. Furthermore, to achieve specific conveying purposes, the helical section can be made of special wear-resistant materials or special wear-resistant processes. The mortise and tenon structure also enables quick maintenance or replacement, helps reduce the axial length of the screw pump, and brings great convenience to design and use.

[0007] To achieve the above-mentioned purpose, the technical solution of the present invention is: a low-noise three-screw waste oil pump with a mortise and tenon connection structure, adopting a vertical single-suction structure, side inlet and side outlet, and the inlet and outlet flanges are coaxial; comprising a pump body, a motor, a screw bushing, a driving screw, and a driven screw, wherein the driving screw and two driven screws are installed in the screw bushing, and the screw bushing covers the spiral sections of the driving screw and the two driven screws to form a spiral sealing cavity; the axial length of the screw bushing is greater than the spiral meshing part formed by the driving screw and the driven screw, forming a screw bushing inlet cavity and a screw bushing inlet cavity, so that when the liquid enters and exits the spiral sealing cavity, a buffer zone is formed with the pump inlet cavity and the pump outlet cavity, which can reduce vibration and noise; the driving screw and the driven screw adopt a split structure and a mortise and tenon connection, and the spiral section and the axial force balancing part adopt a combination of different materials, which can achieve low cost and high wear resistance.

[0008] Furthermore, the pump body is a large-cavity square pump body with large arc chamfers. An inclined partition plate is arranged in the large-cavity square pump body. The inclined partition plate fits tightly with the screw bushing inclined partition plate on the screw bushing to separate the pump inlet cavity and the pump outlet cavity.

[0009] Furthermore, the active screw is decomposed into an active screw axial force balancing section, an active screw spiral section and a cylindrical pin. The active screw axial force balancing section is provided with a positioning shaft extension, and the active screw spiral section is provided with a positioning shaft hole. The positioning shaft extension and the positioning shaft hole are connected by a transition fit, and the length of the positioning shaft extension is greater than the diameter of the shaft extension to ensure the screw's bending and torsional resistance; after the active screw axial force balancing section and the active screw spiral section are connected in place by mortise and tenon, the cylindrical pin is interference fit into the connected circular hole to achieve axial locking.

[0010] Furthermore, the driven screw is decomposed into a driven screw axial force balancing section, a driven screw spiral section and a cylindrical pin; a positioning shaft hole is provided on the driven screw axial force balancing section, and a positioning shaft extension is provided on the driven screw spiral section. The positioning shaft hole and the positioning shaft extension are connected by a transition fit, and the length of the positioning shaft extension is greater than the diameter of the shaft extension to ensure the screw's bending and torsional resistance; after the driven screw axial force balancing section and the driven screw spiral section are connected in place by mortise and tenon, the cylindrical pin is interference fit into the connected circular hole to achieve axial locking.

[0011] Furthermore, a double-profile side clearance non-strict sealing structure is adopted between the active screw and the two driven screws, that is, the angle values ​​of the active screw semi-circular angle 1 and the active screw semi-circular angle 2 are adjusted to be smaller than 28.8° required for the strict sealing type.

[0012] Furthermore, the first semi-central angle of the active screw and the second semi-central angle of the active screw are both 17°, or the first semi-central angle of the active screw is 17° and the second semi-central angle of the active screw is 28.8°.

[0013] The beneficial effects of the present invention are:

[0014] 1. The theoretical pulsation rate is zero, and the actual pulsation is extremely small. It is suitable for low-noise and low-vibration transportation of lubricating media with various viscosity liquids in gas-containing state and solid particles of a certain size;

[0015] 2. The process is adjusted according to the gas content and the requirements for conveying different concentrations and particle sizes. It can adapt to gas-liquid-solid mixed conveying conditions under different requirements and meet the requirements of use in harsh environments such as land, ship and aviation.

[0016] 3. The overall structure has fewer parts and is easy to disassemble, assemble and maintain; it runs smoothly with very low vibration and noise, and the single-side clearance and double-side clearance technologies have been verified in practice;

[0017] 4. The low-noise three-screw pump for gas-liquid-solid mixed transportation is very suitable for use in ship environments with small cabin capacity, cramped space, and high requirements on vibration noise, external dimensions and weight. It also has low production costs and very important market economic value.

[0018] 5. The driving and driven screws utilize a mortise and tenon joint, increasing the rigidity of individual components, improving milling and grinding accuracy and reducing scrap rates. Furthermore, the axial force balance section remains intact at any lead helix angle. Furthermore, the screw section and axial force balance section can be assembled using different materials, reducing costs or enabling specific conveying purposes. Furthermore, the mortise and tenon joint structure allows for rapid maintenance or replacement, reducing the axial length of the screw pump and significantly facilitating design and use.

[0019] In summary, the present invention is suitable for low-noise transportation of dirty oil media in a gas-containing and particle-containing state; it has the advantage of universal design, is applicable to both low-pressure and high-pressure transportation, runs smoothly, and has very little vibration and noise; the active screw and the driven screw are designed and processed in a split type and connected in a mortise and tenon type, which solves the problem of the axial force balance part being destroyed, and the spiral section and the axial force balance part are made of different materials, which can achieve the comprehensive benefits of low cost and high wear resistance, and is conducive to rapid maintenance and replacement, reducing the axial length of the screw pump; the present invention is very suitable for use in environments where space is cramped and small, and there are high requirements for low-noise transportation, rapid maintenance and replacement of gas-containing and particle-containing media, and external dimensions and weight, and it has very important market economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic cross-sectional view of a low-noise three-screw waste oil pump for gas-liquid-solid mixed transport according to the present invention;

[0021] Figure 2 for Figure 1 DD cross-sectional view in;

[0022] Figure 3 This is a schematic diagram of the axial force balance and structure of a three-screw pump;

[0023] Figure 4 Schematic diagram of the active screw mortise and tenon connection structure;

[0024] Figure 5 Schematic diagram of the mortise and tenon connection structure of the driven screw;

[0025] Figure 6 This is a schematic diagram of the screw end face and internal flow channel of a strictly sealed three-screw pump;

[0026] Figure 7 This is the implementation diagram of the double-sided non-strictly sealed screw;

[0027] Figure 8 This is the implementation diagram of a single-side non-strictly sealed screw. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] like Figure 1As shown in Figure 2, a low-noise three-screw pump for mixed gas-liquid-solid transportation of the present invention adopts a vertical single-suction structure, with side inlet and side outlet, and the inlet and outlet flanges are coaxial. After the active screw 8 is fitted with a deep groove ball bearing 5 and locked with a shaft retaining ring, it is installed into the screw bushing 7 together with the driven screw 1 9 and the driven screw 2 10, and then the whole is connected to the connecting frame 3 and tightened; the containerized mechanical seal 4 passes through the active screw 8 and is installed in place on the connecting frame 3; the assembled connecting frame 3 is hoisted into the pump body 6 equipped with a built-in safety valve 11 to complete the assembly of the three-screw pump; then the elastic pin coupling 2 and the motor 1 are installed and connected and tightened. During operation, the motor 1 drives the active screw 8 through the elastic pin coupling 2. The pump body inclined partition plate 61 on the pump body 6 and the screw bushing inclined partition plate 71 on the screw bushing 7 are tightly matched to separate the pump inlet cavity 31 and the pump outlet cavity 33. The screw bushing 7 encases the spiral sections of the active screw 8, driven screws 1 9, and driven screws 2 10, forming a spiral seal chamber. The axial length of the screw bushing 7 is left with excess space, forming screw bushing inlet cavities 32 and 34. This creates a buffer zone with the pump inlet and outlet cavities 31 and 33 when liquid enters and exits the spiral seal chamber, facilitating vibration and noise reduction. For easier reading, the DD view is cut along the pump inlet and outlet axes to reveal the meshing of the screw end faces.

[0030] like Figure 3 As shown, during normal operation, under the influence of the outlet chamber pressure, the driving screw 8 is subjected to a downward force F555 and an upward force F151 along the axis. The driven screw 1 9 is subjected to a downward force F656 and an upward force F353 along the axis. The driven screw 2 10 is subjected to a downward force F454 and an upward force F252 along the axis. Because the axial force balancing components of the driven screws 1 9 and 2 10 and the driving screw 8 utilize a slot-type structure, when combined, the axial force and the weight of all the screws cancel each other out, with the remaining axial force being borne by the deep groove ball bearing 5. This axial force balancing structure is relatively simple. The force distribution shows that all three screws are in a tensile state, which promotes the operational reliability of the slender rod structure.

[0031] like Figure 4 As shown, the present invention adopts an active screw mortise and tenon connection structure, and the active screw 8 is decomposed and designed into an active screw axial force balancing section 81, an active screw spiral section 83 and a cylindrical pin 82. The active screw axial force balancing section 81 is designed with a positioning shaft extension 84, and the active screw spiral section 83 is designed with a positioning shaft hole 85. The two are designed with a transition fit, and the length of the shaft extension is required to be greater than the diameter of the shaft extension to ensure the screw's bending and torsion resistance; after the active screw axial force balancing section 81 and the active screw spiral section 83 are mortise and tenon connected in place, the cylindrical pin 82 is interference fit into the circular hole after the connection to achieve axial locking.

[0032] The present invention decomposes the active screw into an active screw axial force balancing section 81 and an active screw helical section 83 with a mortise and tenon joint structure. These sections are machined separately, thus avoiding damage to the axial force balancing section during milling and grinding. Furthermore, after the slender structure is shortened, the rigidity of each section is increased, facilitating machining and reducing scrap rates. Furthermore, the active screw axial force balancing section 81 and the active screw helical section 83 can be made of different materials, either to save costs or to achieve special purposes. For example, using carbon steel for the active screw axial force balancing section 81 and alloy steel for the active screw helical section 83 can save costs. Using copper alloy for the active screw helical section 83 can facilitate the transport of some special media.

[0033] like Figure 5 As shown in (a) and (b), the moving screw has a mortise and tenon connection structure, and the driven screw 1 9 and the driven screw 2 10 are exactly the same parts, so only the driven screw 1 9 is described as an example here.

[0034] Figure 5 (a), (b) The driven screw rod 9 is decomposed and designed into a driven screw rod axial force balancing section 91, a driven screw helical section 93 and a cylindrical pin 92; a positioning shaft hole 94 is designed on the driven screw rod axial force balancing section 91, and a positioning shaft extension 95 is designed on the driven screw helical section 93. The two adopt a transition fit design, and the length of the shaft extension is required to be greater than the diameter of the shaft extension to ensure the bending and torsion resistance of the screw; after the driven screw rod axial force balancing section 91 and the driven screw rod helical section 93 are connected in place by mortise and tenon, the cylindrical pin 92 is interference fit into the circular hole after the connection to achieve axial locking. The present invention decomposes the driven screw into an axial force balancing section 91 and a helical section 93 with a mortise and tenon joint structure. These sections are machined separately, avoiding damage to the axial force balancing section during milling or grinding. Furthermore, the axial force balancing section 91 and the helical section 93 can be made of different materials, either to save costs or to achieve specific uses. For example, using carbon steel for the axial force balancing section 91 and alloy steel for the helical section 93 can save costs. Using copper alloy for the helical section 93 can facilitate the transport of certain special media.

[0035] Figure 6 The schematic diagram is a schematic diagram of the screw end face and internal flow channel of a strictly sealed three-screw pump, which is only used as a reference in this application and does not belong to the scope of application of the present invention.

[0036] The semi-center angles of the driving screw (-24), driving screw (-25), and driven screw (-21, 23) are all 28.8° (0.16π), which is the basic characteristic of screw parameters for strict sealing. The driven screw rotates automatically under the inlet and outlet pressure differential. The driving and driven screws only experience relative rotational motion, without torque transmission. Therefore, screw surface wear is extremely minimal, and three-screw pumps generally operate with low noise. However, when the conveying medium contains a certain amount of insoluble gas, the gas drawn into the inlet chamber enters the outlet chamber through the spiral flow channel formed by the screw. The moment the outlet chamber opens, the gas in the spiral seal chamber is rapidly compressed or collapsed by the high pressure of the outlet chamber. The resulting compression and collapse of numerous bubbles significantly affects the smooth delivery of the medium and pressure pulsation. The waste oil pump produces a loud noise and vibration, with a loud "crackling" sound audible to the ear, seriously affecting the vibration and noise performance of the three-screw pump. This indicates that the strictly sealed screw design of a three-screw pump can no longer maintain low noise and vibration operation in this gas-liquid mixed transmission condition. Similarly, solid particles of a certain size in the medium can enter the spiral seal chamber and be transferred from the inlet cavity to the outlet cavity. However, if the solid particles enter the spiral surface during the meshing process, they are likely to cause jamming and shaft seizure.

[0037] There are two main implementation plans for the non-sealed screw structure of the low-noise three-screw pump for gas-liquid-solid mixed transportation.

[0038] Figure 7 This is a three-screw pump double-sided non-strictly sealed screw implementation diagram, the active screw semi-center angle 1 24 and the active screw semi-center angle 2 25 are both 17°, and 17° is an exemplary embodiment. Figure 7 Another embodiment is a three-screw pump with a single-side non-strictly sealed screw, wherein the active screw semi-center angle 1 24 is 17° and the active screw semi-center angle 25 is 28.8°.

[0039] The overall structural design considerations of the present invention lay a good foundation for low-noise gas-liquid-solid mixed transportation, and the main innovations are: ① The designed large arc chamfered square pump body 6 has the advantage of a large cavity, which is conducive to maintaining the overall flow field speed at a low state; ② The design adopts a lower rotation speed to keep the rotational linear speed of the active screw 8 and the driven screws one, two 9, and 10 at a low state; ③ The axial length of the screw bushing 7 is greater than the spiral meshing part formed by the active screw 8 and the driven screws one, two 9, and 10, or the screw bushing 7 covers the spiral meshing part, thereby forming a screw bushing inlet cavity 32 and a screw bushing outlet cavity 34. The appearance of these two cavities can be regarded as a buffer zone for the medium to enter and flow out of the spiral meshing part, which reduces the interference of the spiral flow channel on the pump body inlet cavity 31 and the pump body outlet cavity 34 to a certain extent, and is conducive to low-noise operation. The above measures have created good conditions for low-noise operation under gas-liquid-solid mixed transportation conditions, but the processing of the transportation of particles of a certain size in the gas and medium in the spiral sealing cavity is the design content that the present invention focuses on. The design method of the present invention is a non-strict sealing structure of the profile side clearance: that is, adjusting the angle value of the semi-center angle of the active screw -24 and the semi-center angle of the active screw -25 to be less than the 28.8° required for the strict sealing type. Reduction of the semi-center angle. After the profile side clearance of the active screw and the driven screw is significantly increased, the strict sealing structure can no longer be achieved, so that the amount of return oil of the high-pressure oil in the outlet cavity introduced into the screw sealing cavity along the profile side clearance of the active screw is significantly increased, thereby realizing the pre-compression of the gas in the screw sealing cavity. When the gas in the screw sealing cavity is transferred to the outlet cavity, there will be no instantaneous burst, thereby achieving the purpose of low noise and low vibration. Similarly, the significant increase in profile side clearance not only provides a buffer for conveying solids of a certain size, but also, when the solid particles are in the process of meshing and biting the helical surface, the profile side clearance and the presence of the profile helical surface slope will cause the solid particles in the process to break away from the biting surface, thereby reducing the probability of sticking and shaft seizure. Because the dirty oil has a certain lubricity, the solid particles are immersed in it, and the solid particle surface has a certain lubricating property, which also facilitates the realization of gas-liquid-solid mixed transportation.

[0040] Figure 7 、 Figure 8 In the schematic diagram, the driven screw semi-center angles 21 and 23 are both 28.8° (0.16π), and the driving screw semi-center angle 1 24 and the driving screw semi-center angle 2 25 are either 17° or both. Figure 7 、 Figure 8The semi-center angles of the active screw (-24) and (-25) are adjusted according to the requirements of the gas-liquid mixed transport, with an adjustment range of 0 to 28.8° and not limited to the example value of 17°. The advantages of the non-strictly sealed side clearance structural design are threefold: ① The oil inlet channel is naturally formed along the screw profile, resulting in a smooth profile with no sharp edges; ② The driven screw has lower rigidity than the active screw and is more difficult to machine. The angle of the driven screw's top circle remains unchanged, unaffecting its automatic rotation effect and providing excellent general performance; ③ The semi-center angles of the active screw (-24) and (-25) are adjustable within a range of 0 to 28.8°, enabling different oil inlet volumes to accommodate gas-liquid-solid mixed transport with varying gas contents and solid particle sizes.

Claims

1. A low-noise three-screw sewage oil pump with a mortise and tenon joint structure, adopting a vertical single-suction structure, side inlet and side outlet, and coaxial inlet and outlet flanges, characterized by: It includes a pump body, an electric motor, a screw bushing, a driving screw and a driven screw. The driving screw and two driven screws are installed in the screw bushing. The screw bushing covers the spiral sections of the driving screw and the two driven screws to form a spiral sealing chamber. The axial length of the screw bushing is greater than the spiral meshing part formed by the driving screw and the driven screw, forming a screw bushing inlet cavity and a screw bushing inlet cavity, so that when the liquid enters and exits the spiral sealing chamber, a buffer zone is formed with the pump inlet cavity and the pump outlet cavity, which can reduce vibration and noise. The driving screw and the driven screw adopt a split structure and a mortise and tenon connection. The spiral section and the axial force balancing part adopt a combination of different materials, which can achieve low cost and high wear resistance.

2. The low-noise three-screw waste oil pump with a mortise and tenon joint structure according to claim 1, characterized in that: The pump body is a large-cavity square pump body with large arc chamfers. An inclined partition plate is arranged in the large-cavity square pump body. The inclined partition plate closely cooperates with the screw bushing inclined partition plate on the screw bushing to separate the pump inlet cavity and the pump outlet cavity.

3. The low-noise three-screw sewage oil pump with a mortise and tenon joint structure according to claim 1 is characterized in that: The active screw is decomposed into an active screw axial force balancing section, an active screw spiral section and a cylindrical pin. The active screw axial force balancing section is provided with a positioning shaft extension, and the active screw spiral section is provided with a positioning shaft hole. The positioning shaft extension and the positioning shaft hole are connected by a transition fit, and the length of the positioning shaft extension is greater than the diameter of the shaft extension to ensure the bending and torsion resistance of the screw; after the active screw axial force balancing section and the active screw spiral section are connected in place by mortise and tenon, the cylindrical pin is interference fit into the connected circular hole to achieve axial locking.

4. The low-noise three-screw sewage oil pump with a mortise and tenon joint structure according to claim 1, characterized in that: The driven screw is decomposed into a driven screw axial force balancing section, a driven screw spiral section and a cylindrical pin; a positioning shaft hole is provided on the driven screw axial force balancing section, and a positioning shaft extension is provided on the driven screw spiral section. The positioning shaft hole and the positioning shaft extension are connected by a transition fit, and the length of the positioning shaft extension is greater than the diameter of the shaft extension to ensure the bending and torsion resistance of the screw; after the driven screw axial force balancing section and the driven screw spiral section are connected in place by mortise and tenon, the cylindrical pin is interference fit into the connected circular hole to achieve axial locking.

5. The low-noise three-screw waste oil pump with a mortise and tenon joint structure according to claim 1, characterized in that: A double-surface side clearance non-strict sealing structure is adopted between the active screw and the two driven screws, that is, the angle values ​​of the active screw semi-circular center angle 1 and the active screw semi-circular center angle 2 are adjusted to be smaller than 28.8° required for the strict sealing type.

6. The low-noise three-screw sewage oil pump with a mortise and tenon joint structure according to claim 5, characterized in that: The first semi-circular center angle of the active screw and the second semi-circular center angle of the active screw are both 17°, or the first semi-circular center angle of the active screw is 17° and the second semi-circular center angle of the active screw is 28.8°.

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