Stainless steel welding rotor of roots vacuum pump

Abstract

The stainless steel welded rotor of the roots vacuum pump comprises a stainless steel driving rotor and a stainless steel driven rotor which are identical in structure, the driving rotor comprises a driving shaft and a driving impeller, the driving shaft is sleeved with the driving impeller, the driven rotor comprises a driven shaft and a driven impeller, the driven shaft is sleeved with the driven impeller, and the driven shaft is sleeved with the driven impeller. The driving rotor and the driven rotor are vertically distributed in the pump shell at 90 degrees and are meshed with each other; the middle of the driving shaft is sleeved with a first welding sleeve and a second welding sleeve which are connected front and back, a plurality of key grooves are formed in the surface of the driving shaft, key grooves are formed in inner holes of the first welding sleeve and the second welding sleeve, and flat keys are arranged in the key grooves and used for the driving shaft to transmit torque to the main impeller. The main impeller comprises two curved surface type plates, and a plurality of reinforcing rib plates which are arranged at equal intervals are arranged in the main impeller. The vacuum pump has the advantages of corrosion resistance, high yield, light weight, high strength, no internal stress, high overall precision and the like, and the vacuum pump is not easy to deform when running under high-temperature and high-pressure conditions.

Description

Technical Field

[0001] The utility model relates to the technical field of Roots vacuum pumps, in particular to a Roots vacuum pump stainless steel welded rotor. Background Art

[0002] In recent years, the demand for Roots vacuum pumps in the fields of chemical industry, pharmaceuticals, etc. has been increasing. Since most of the process gases in the chemical and pharmaceutical industries contain corrosive gases, and ordinary material Roots vacuum pumps cannot meet the needs of such corrosive processes, it is necessary to manufacture corrosion-resistant Roots vacuum pumps to meet the requirements of the above special processes. Although stainless steel is the preferred material for corrosion resistance requirements, there are many difficult problems to overcome in the blank casting and precision machining processes of stainless steel materials. Since the length of the Roots vacuum pump rotor is relatively long and in order to reduce the rotational inertia of the rotor and lower the starting load of the Roots vacuum pump, the inside of the rotor must be made into a hollow structure, so the yield rate of stainless steel rotors by casting is very low, and there are many casting defects. Therefore, there is no stainless steel Roots vacuum pump on the market at present. The cast iron blanks of existing Roots vacuum pumps are obtained by casting, and then the cast iron blank parts are processed into the dimensions and precisions required for the vacuum pump by numerical control machining equipment.

[0003] Ordinary cast iron materials are not chemically corrosion-resistant. In order to meet the needs of the chemical and pharmaceutical industries for corrosion-resistant vacuum equipment, an anti-corrosion coating is usually applied to the inner surface of the parts in the gas flow-through part of the Roots vacuum pump to meet the corrosion resistance requirements of the chemical and pharmaceutical industries. At present, due to the limitation of the coating processing technology level, the surface anti-corrosion coating can only be about 0.03 mm. Since the anti-corrosion coating is relatively thin, the anti-corrosion coating is prone to short-term failure phenomena such as coating disappearance, peeling, and corrosion when the Roots vacuum pump is used in a strongly corrosive working condition, which affects the pumping performance of the Roots vacuum pump, and the uneven coating thickness will also affect the normal operation of the Roots vacuum pump.

[0004] The rotor is a key part with a relatively complex internal structure and high precision requirements in the Roots vacuum pump. One of the difficulties of the corrosion-resistant stainless steel Roots vacuum pump is the manufacture of a pair of mutually meshing stainless steel rotors inside it. In order to solve the corrosion resistance problem of the Roots vacuum pump in the chemical and pharmaceutical industries, the applicant proposes a Roots vacuum pump stainless steel welded rotor, which is applied to the Roots vacuum pump. Summary of the Invention

[0005] The purpose of the utility model is to overcome the above deficiencies and provide a Roots vacuum pump stainless steel welded rotor to solve the corrosion resistance problem of the Roots vacuum pump in the chemical process.

[0006] The purpose of the utility model is achieved as follows:

[0007] A stainless steel welded rotor for a Roots vacuum pump, which includes a stainless steel driving rotor and a stainless steel driven rotor with the same structure. The driving rotor includes a driving shaft and a main impeller, and the main impeller is sleeved on the driving shaft. The driven rotor includes a driven shaft and a driven impeller, and the driven impeller is sleeved on the driven shaft. The driving rotor and the driven rotor are vertically distributed at 90° in the pump housing and mesh with each other;

[0008] A first welding sleeve and a second welding sleeve are sleeved in the middle of the driving shaft. The first welding sleeve and the second welding sleeve are arranged front and back and welded at one end. A plurality of key grooves are provided on the surface of the driving shaft. Key grooves are provided in the inner holes of the first welding sleeve and the second welding sleeve. The key groove positions of the first welding sleeve and the second welding sleeve match the corresponding key grooves on the driving shaft. A flat key is arranged inside the key groove for the driving shaft to transmit torque to the main impeller. The main impeller includes two curved-shaped plates, and the two plates form an 8-shaped curved surface axially. A plurality of equally spaced reinforcing rib plates are arranged inside the main impeller;

[0009] The structure of the driven shaft is the same as that of the driving shaft, and the structure of the driven impeller is the same as that of the main impeller.

[0010] Further, the driving shaft includes a slender shaft composed of a plurality of cylindrical shaft bodies with different shaft diameters. The cylindrical shaft body with the largest shaft diameter is arranged at the central position of the driving shaft, and the shaft diameters of the other cylindrical shaft bodies decrease symmetrically in sequence from both sides of the axis.

[0011] Further, the opposite ends of the first welding sleeve and the second welding sleeve are continuously welded in a full circle and connected to the driving shaft through a tapered pin.

[0012] Further, the rib plate is sleeved outside the first welding sleeve and the second welding sleeve, and the outer edge of the rib plate fits against the inner side wall of the plate.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] The present invention provides a stainless steel welded rotor for a Roots vacuum pump. Each rotor is composed of 5 groups of part module units: main shaft, plate, shaft sleeve, rib plate, and flat key. Since the strength of the stainless steel plate is much higher than that of a cast iron part with the same thickness, a number of reinforcing ribs are evenly arranged inside the rotor plate to increase the strength of the rotor. In this way, the wall thickness of the part module units constituting the rotor is greatly reduced, thereby greatly reducing the weight of the rotor and saving material costs. The present invention has the advantages of high finished product rate, light weight, good heat dissipation, high strength, no internal stress, high overall accuracy, good dynamic balance, good part stability, and the vacuum pump is not prone to deformation when operating under high temperature and high pressure conditions. Description of the Drawings

[0015] Figure 1 It is a schematic assembly structure diagram of the driving and driven rotors of the present invention.

[0016] Figure 2 The structural schematic diagram of the driving rotor of the present utility model.

[0017] Figure 3 The structural schematic diagram of the driven rotor of the present utility model.

[0018] Figure 4 The sectional schematic diagram of the rotor of the present utility model.

[0019] Figure 5 The side schematic diagram of the rotor of the present utility model.

[0020] Wherein:

[0021] Driving rotor 1, driving shaft 2, first welding sleeve 2.1, flat key 2.2, tapered pin 2.3, second welding sleeve 2.4, main impeller 3, template 3.1, rib plate 3.2, driven rotor 4, driven shaft 5, slave impeller 6. Specific embodiments

[0022] To better understand the technical solution of the present utility model, the following will be described in detail in conjunction with relevant drawings. It should be understood that the following specific embodiments are not intended to limit the specific implementation aspects of the technical solution of the present utility model, but are only the implementation aspects that the technical solution of the present utility model can adopt. It should be noted first that the description of the positional relationship of each component herein, such as component A is located above component B, is based on the relative positions of the components in the drawings and is not intended to limit the actual positional relationship of each component. Embodiment 1

[0023] See Figures 1 - 5 , Figure 1 , a structural schematic diagram of the present utility model is drawn. As shown in the figure, a Roots vacuum pump stainless steel welded rotor involved in the present utility model includes a driving rotor 1 and a driven rotor 4 with the same structure. The driving rotor 1 includes a driving shaft 2 and a main impeller 3. The main impeller 3 is sleeved on the driving shaft 2. The driven rotor 4 includes a driven shaft 5 and a slave impeller 6. The slave impeller 6 is sleeved on the driven shaft 5. The driving rotor 1 and the driven rotor 4 are vertically distributed at 90°, and mesh with each other in the pump housing with a certain gap, and rotate in opposite directions through synchronous gear transmission to realize the suction and exhaust functions of the Roots vacuum pump.

[0024] The driving shaft 2 includes a slender shaft composed of several cylindrical shaft bodies with different shaft diameters. The cylindrical shaft body with the largest shaft diameter is arranged at the central position of the driving shaft 2, and the shaft diameters of the other cylindrical shaft bodies decrease symmetrically in sequence from both sides, with the surface presenting a trapezoidal stepped shape; multiple key grooves are provided on the surface of the driving shaft 2, and flat keys 2.2 are arranged in the key grooves. A first welding sleeve 2.1 and a second welding sleeve 2.4 are sleeved on the shaft body with the largest shaft diameter of the driving shaft 2. The first welding sleeve 2.1 and the second welding sleeve 2.4 are arranged front and back and are welded at one end. Key grooves are provided in the inner holes of the first welding sleeve 2.1 and the second welding sleeve 2.4, and corresponding key grooves matching the key grooves of the first welding sleeve 2.1 and the second welding sleeve 2.4 are also provided at the corresponding positions on the driving shaft 2. Flat keys 2.2 are arranged inside the key grooves for the driving shaft 2 to transmit torque to the main impeller 3.

[0025] One end of the first welding sleeve 2.1 and the second welding sleeve 2.4 that face each other are continuously welded in the full circumference and are connected to the driving shaft 2 through a taper pin 2.3.

[0026] The main impeller 3 includes two curved type plates 3.1. The two type plates 3.1 form a figure-eight curved surface axially. Six equally spaced reinforcing rib plates 3.2 are arranged inside the main impeller 3. The rib plates 3.2 are sleeved outside the first welding sleeve 2.1 and the second welding sleeve 2.4, and the outer edges of the rib plates 3.2 are attached to the inner side walls of the type plates 3.1.

[0027] The structure of the driven shaft 5 is the same as that of the driving shaft 2, and the structure of the driven impeller 6 is the same as that of the main impeller 3.

[0028] All the above components constituting the driving rotor 1 and the driven rotor 4 are made of stainless steel.

[0029] A Roots vacuum pump stainless steel welded rotor involved in this embodiment has the following manufacturing process:

[0030] Place the driving shaft on two V-shaped iron welding jigs; put the two welding shaft sleeves into a heating oven and heat them to 200 °C and keep them warm for 15 min, then sequentially heat-sleeve the heated welding shaft sleeves onto the corresponding positions of the driving shaft from left to right or from right to left. The shaft sleeve and the shaft diameter have an interference fit, so that the shaft sleeve is shrink-fixed to the driving shaft after cooling.

[0031] After the shaft sleeve is completely cooled, use a positioning jig to place 6 rib plates on the two welding shaft sleeves in sequence, and then weld the two shaft sleeves together; the welding must be a bilateral full-circumference continuous weld, and there shall be no incomplete welds or missed welds in the middle. After welding, clean up impurities such as welding slag, then drill and ream the taper pin holes and insert taper pins. Press the taper pins from the larger end and then weld the taper pins firmly to the shaft sleeve.

[0032] Before welding, first check the accuracy of the joint between the two curved templates and the rib plates. Symmetric welding can be carried out in sections according to the actual situation, but the welding firmness must be ensured. To increase the welding firmness, it is allowed to drill holes with a diameter of ∅12mm and a depth of 18mm in the middle of the rib plates aligned outside the template, and evenly punch holes at intervals of 80 - 100mm along the circumference. Then, weld firmly, penetrate, and fill the hole cavity without leakage. After all welding is completed, stability annealing treatment must be carried out.

[0033] After the heat treatment of the rotor, shot peening is carried out. After the welded parts pass the secondary inspection and are qualified, they enter the precision machining process. After all precision machining is completed, the residue in the rotor inner cavity is removed, and then a dynamic balance test is carried out. The unbalance amount < 120g.cm. It is allowed to weld counterweight blocks on the non-machined surface of the rotor inner cavity to obtain dynamic balance. The welded counterweight blocks must be firm and not fall off.

[0034] Overall assembly welding process of the rotor:

[0035] Select suitable welding materials: According to the use environment and performance requirements, select suitable welding wire materials and ensure the matching of the welding materials with the base metal; for example, 304 stainless steel is suitable for general environments, while 316 stainless steel has better corrosion resistance and is suitable for strongly corrosive chemical environments.

[0036] Clean the surface: To ensure product quality, the surface of the stainless steel workpiece must be thoroughly cleaned before welding. The stainless steel surface is easily contaminated by grease, oxides, and other impurities, and these contaminants will cause weld defects during welding.

[0037] Preheating and temperature control: Although most stainless steels can be welded at room temperature, some thick plates or stainless steels with high carbon content need preheating during welding; preheating can reduce welding stress and prevent crack formation. However, too high preheating temperature may cause intergranular corrosion and the formation of precipitates.

[0038] Welding process and parameter setting: Selecting suitable welding processes and parameters is crucial for stainless steel welding; according to the structure of the Roots vacuum pump body, the gas shielded welding method with secondary welding is required, that is, first perform overall backing welding and then overall capping welding; Gas shielded welding has the advantages of fast welding speed, stable quality, and low cost, and is suitable for welding parts with a high density distribution.

[0039] Shielding gas: For the welding area that needs to be protected, shielding gases such as argon and nitrogen should be used to prevent oxidation and nitridation; the purity and flow rate of the shielding gas should be adjusted according to the welding current and welding position.

[0040] Check the weld quality: After welding, the welds need to be inspected for appearance and non-destructive testing to ensure welding quality and safety; for welds with unqualified appearance, repair or rework is required.

[0041] Working principle:

[0042] The Roots vacuum pump housing contains a pair of figure-eight rotors that rotate in reverse synchronously. The two rotors are respectively fixed on two parallel main and driven shafts, and are driven to rotate in opposite directions by a pair of gears with a transmission ratio of 1. The surfaces of the two rotors mesh with each other at a certain gap, and there is also a certain gap between the rotors and the inner wall of the pump housing, which allows the Roots vacuum pump to operate at a high speed. The working principle of the Roots vacuum pump is based on the continuous rotation of the two rotors. Gas is sucked into the space between the rotor and the pump housing from the suction port, and then the gas is discharged from the exhaust port through the rotation of the rotor.

[0043] The main and driven stainless steel welded rotors are respectively composed of several shaft sleeves, several rib plates and two housing components that form the rotor surface by welding. Since there is a pressure difference of up to 100 kPa between the inlet and outlet ports during the operation of the Roots vacuum pump, the pressure acting on the upper and lower sides of a single rotor reaches more than 20 kN. This requires that the rotor has sufficient strength to withstand the high pressure difference on both sides and at the same time reduce the rotor mass to lower the power consumption during the operation of the Roots vacuum pump.

[0044] Since the Roots vacuum pump rotor has a slender structure with a large ratio of diameter to length and needs to be hollowed out inside and has many reinforcing rib plates arranged, the external curved surface shape of the rotor is relatively complex. If the stainless steel casting method is used, the qualified rate of stainless steel blank castings is very low. For large-scale production, a low yield means more material loss and higher production costs. The key factor affecting the quality of the stainless steel rotor is that due to the poor fluidity of the stainless steel molten metal during casting, shrinkage holes, missing corners, rough surfaces, internal pores, a large number of cracks and other casting defects are likely to appear in the thin-walled parts, and the qualified rate of the castings cannot be controlled, which affects the normal production of the product and greatly increases the manufacturing cost of the product.

[0045] The utility model decomposes the main and driven rotors of the Roots vacuum pump into several part module units respectively. Using corresponding cutting, welding and machining equipment, each module unit is processed to the corresponding blank size according to the drawings and technical requirements. Then, the part module units of the main and driven rotors are welded into a rotor blank by welding method, the welding stress of the rotor is eliminated by heat treatment, and finally a pair of stainless steel corrosion-resistant Roots vacuum pump rotors are obtained through precision machining by numerical control equipment. Since the strength of the stainless steel plate is much higher than that of cast iron parts with the same thickness, and furthermore, several reinforcing ribs are evenly arranged inside the rotor template to increase the strength of the rotor, the wall thickness of the part module units that make up the rotor can be reduced a lot, thus greatly reducing the weight of the rotor and saving the material cost.

[0046] Use a water jet cutting device to cut the 6 reinforcing rib plates inside the impeller to the corresponding dimensions and shapes according to the design drawings, and then use the corresponding cutting and processing equipment to prepare the welding bevels according to the design drawings. The housing of the impeller is an irregular figure-eight curved surface. According to the curved surface development drawing, use a water jet cutting machine for blanking, and then use a hydraulic press and a mold to press the stainless steel plate into the curved surface shape required for the impeller housing, and prepare the welding bevels at the welds.

[0047] The above are only specific application examples of the present utility model, and do not constitute any limitation to the protection scope of the present utility model. Any technical solutions formed by equivalent transformation or equivalent substitution fall within the scope of the protection of the rights of the present utility model.

Claims

1. A stainless steel welded rotor of a Roots vacuum pump, characterized in that: It includes a stainless steel driving rotor (1) and a stainless steel driven rotor (4) with the same structure. The driving rotor (1) includes a driving shaft (2) and a main impeller (3). The main impeller (3) is sleeved on the driving shaft (2). The driven rotor (4) includes a driven shaft (5) and a driven impeller (6). The driven impeller (6) is sleeved on the driven shaft (5). The driving rotor (1) and the driven rotor (4) are vertically distributed at 90° in the pump casing and mesh with each other. A first welding sleeve (2.1) and a second welding sleeve (2.4) are sleeved in the middle of the driving shaft (2). The first welding sleeve (2.1) and the second welding sleeve (2.4) are arranged front and back and welded at one end. A plurality of key grooves are provided on the surface of the driving shaft (2). Key grooves are provided in the inner holes of the first welding sleeve (2.1) and the second welding sleeve (2.4). The key groove positions of the first welding sleeve (2.1) and the second welding sleeve (2.4) match the key grooves at the corresponding positions on the driving shaft (2). A flat key (2.2) is arranged inside the key grooves for the driving shaft (2) to transmit torque to the main impeller (3). The main impeller (3) includes two curved templates (3.1). The two templates (3.1) form a figure-eight curved surface axially. A plurality of equally spaced reinforcing rib plates (3.2) are arranged inside the main impeller (3). The structure of the driven shaft (5) is the same as that of the driving shaft (2), and the structure of the driven impeller (6) is the same as that of the main impeller (3).

2. The stainless steel welded rotor of a Roots vacuum pump according to claim 1, wherein: The driving shaft (2) includes a slender shaft composed of a plurality of cylindrical shaft bodies with different shaft diameters. The cylindrical shaft body with the largest shaft diameter is arranged at the central position of the driving shaft (2), and the shaft diameters of the other cylindrical shaft bodies decrease symmetrically in sequence from both sides.

3. The stainless steel welded rotor of a Roots vacuum pump according to claim 1, characterized in that: The opposite ends of the first welding sleeve (2.1) and the second welding sleeve (2.4) are continuously welded in a full circle and connected to the driving shaft (2) through a taper pin (2.3).

4. A Roots vacuum pump stainless steel welded rotor according to claim 1, characterized in that: The rib plate (3.2) is sleeved outside the first welding sleeve (2.1) and the second welding sleeve (2.4), and the outer edge of the rib plate (3.2) is attached to the inner side wall of the template (3.1).

Images