A bypass Roots pump

Abstract

The present invention provides a bypass Roots pump, comprising: a pump housing having a hollow inner cavity; two rotors that mesh with each other and are rotatably disposed in the hollow inner cavity, dividing the hollow inner cavity into an intake cavity and an exhaust cavity; the pump housing is provided with a first channel and a second channel; the first channel communicates with one of the intake cavity and the exhaust cavity, and the second channel communicates with the other of the intake cavity and the exhaust cavity; a plurality of first one-way valves are arranged in parallel between the first channel and the second channel; the flow direction of the first one-way valve is from the exhaust cavity to the intake cavity; at least two of the first one-way valves have different opening pressures. It overcomes the defect of the existing bypass Roots pump that causes difficulties in use because its protection pressure and bleed-off flow rate do not have a gradient, enabling the protection pressure and bleed-off flow rate to have a corresponding gradient, preventing the Roots pump from overheating and being damaged, and weakening the negative impact of bypass protection on the pumping efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of vacuum pumping equipment, and particularly relates to a bypass Roots pump. Background Art

[0002] The advantage of a Roots vacuum pump is that it has a high pumping speed at a relatively low inlet pressure. However, when the difference between the outlet pressure and the inlet pressure is too large, the Roots pump will overheat, causing the rotor to expand and jam, and the motor to burn out. Therefore, a Roots pump usually cannot be used alone and must be connected in series with a fore-vacuum pump. The Roots pump can only start working when the pressure in the system to be pumped is reduced by the fore-vacuum pump to the allowable inlet pressure of the Roots pump, and it is not allowed to work under a large pressure difference to avoid overload and overheating damage. However, during use, due to the mismatch between the operation of the front and rear stages of the pump or other unexpected situations, the Roots pump sometimes still faces a large pressure difference condition. Therefore, in order to achieve protection, a bypass valve is set from the exhaust end to the suction end to weaken the pressure difference.

[0003] However, if the bypass protection of the existing bypass Roots pump is too sensitive, that is, the opening pressure is low and the bleed flow rate is large, the bypass valve will open due to occasional surging of the air flow, resulting in unstable air pressure, and a large amount of the already pumped air will flow back into the suction end, reducing the overall pumping efficiency of the system; while if the bypass protection is relatively insensitive, that is, the opening pressure is high or the bleed flow rate is small, although the problem of the bypass valve opening due to occasional surging and the reduction of the pumping efficiency caused by bypass protection is avoided, the probability of the occurrence of a large pressure difference condition is increased, and the possibility of overheating and damage of the Roots pump is increased. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect that the existing bypass Roots pump has a usage dilemma due to the lack of gradient in its protection pressure and bleed flow rate.

[0005] To solve the above technical problem, the present application provides a bypass Roots pump, including:

[0006] A pump housing having a hollow inner cavity;

[0007] Two rotors that mesh with each other and are rotatably arranged in the hollow inner cavity, dividing the hollow inner cavity into an intake cavity and an exhaust cavity;

[0008] The pump housing is provided with a first channel and a second channel; the first channel is communicated with one of the intake cavity and the exhaust cavity, and the second channel is communicated with the other of the intake cavity and the exhaust cavity;

[0009] A plurality of first one-way valves are arranged in parallel between the first channel and the second channel; after the first one-way valve is opened, the flow direction of the gas passing through the first one-way valve is from the exhaust cavity to the intake cavity; at least two of the first one-way valves have different opening pressures.

[0010] Optionally, the pump housing includes:

[0011] A housing main body;

[0012] A bypass plate, which is sealingly connected to the housing main body to enclose the hollow inner cavity; the bypass plate is arranged at the end of the rotor and is rotatably connected to the rotor; the first channel and the second channel are both opened on the bypass plate.

[0013] Optionally, the second channel includes a longitudinal channel that traverses the connection line of the axes of the two rotors, and the first one-way valve is arranged at one end of the longitudinal channel, and the other end of the longitudinal channel is communicated with the intake cavity or the exhaust cavity through an opening.

[0014] Optionally, the second channel further includes a transverse channel that communicates with one end of the longitudinal channel away from the opening and is parallel to the connection line of the axes of the two rotors, the first channel is arranged in parallel with the transverse channel, and the first one-way valve is arranged side by side along the direction of the transverse channel.

[0015] Optionally, the bypass plate includes:

[0016] A cover plate;

[0017] A valve plate; one side of the valve plate is sealingly connected to the housing main body; a first slot is dug on the side of the valve plate facing the housing main body to form the first channel; a second slot is dug on the side of the valve plate facing away from the housing main body and is sealingly connected to the cover plate to form the second channel.

[0018] Optionally, the first channel is located between the transverse channel and the side of the bypass plate.

[0019] Optionally, the first one-way valve includes:

[0020] A stepped hole, which is arranged between the first channel and the second channel;

[0021] A first steel ball, which is placed in the large hole of the stepped hole, and the diameter of the first steel ball is larger than the diameter of the small hole of the stepped hole;

[0022] A one-way valve bolt, which is threadedly connected to the bypass plate through a threaded hole arranged between the first channel and the side of the bypass plate;

[0023] A first spring, which is located between the first steel ball and the one-way valve bolt; the head end of the one-way valve bolt presses the first spring so that the first steel ball abuts against the orifice of the small hole of the stepped hole.

[0024] Optionally, a second one-way valve is arranged between the first channel and the second channel, and the flow direction of the second one-way valve is from the intake cavity to the exhaust cavity.

[0025] Optionally, the second one-way valve includes:

[0026] A directly drawn threaded hole is provided between the first channel and the second channel;

[0027] An external thread sleeve has a central through hole and is threadedly connected to the directly drawn threaded hole;

[0028] A second steel ball has a diameter larger than the diameter of the central through hole and abuts against the edge of the central through hole;

[0029] A second spring is located between the second channel and the second steel ball, and the external thread sleeve compresses the second spring by pressing the second steel ball.

[0030] Optionally, an assembly threaded hole is provided between the first channel and the side of the bypass plate; the diameter of the assembly threaded hole is larger than the outer diameter of the external thread sleeve and faces the directly drawn threaded hole; an internal hexagonal counterbore is provided at one end of the external thread sleeve close to the assembly threaded hole, and a plug is hermetically connected to the assembly threaded hole.

[0031] By adopting the above technical solutions, the present invention has the following technical effects:

[0032] 1. When the bypass Roots pump provided by the present invention is working, no matter what causes the air pressure to slightly increase to the warning value, the first one-way valve with a lower pressure will be opened to play the bypass protection function. However, when the single bypass valve is opened, its flow rate of discharged fluid is relatively small, thus preventing a large amount of the already extracted air flow from flowing back to the intake end again, ensuring that the overall pumping efficiency of the system will not be greatly reduced. At this time, if the external air pressure rises slightly and briefly, then as the pressure difference decreases by itself or passively, the bypass function will be closed, and the pump will re-enter the normal working condition; if it is a situation where the air pressure rises for a relatively long time and by a large margin, then due to the continuity of the air pressure increase, as the air pressure rises, the first one-way valve with a higher pressure arranged in parallel will be triggered to open. With the opening of the second bypass valve, the parallel valve cavities make the flow rate of discharged fluid of the entire device relatively larger, thereby quickly reducing the pressure difference between the two ends of the Roots pump until it is reduced to the point where the one-way valve with a higher opening pressure closes and only the one-way valve with a smaller opening pressure remains open. At this time, the flow rate of discharged fluid becomes smaller to weaken the reduction effect of the bypass protection on the pumping efficiency. Therefore, its protection pressure and discharge flow rate have a gradient, which not only effectively prevents the overload and jamming of the vacuum pump under certain unpredictable working conditions, improves the adaptability and service life of the vacuum pump under complex working conditions, but also weakens the negative impact of the bypass protection on the pumping efficiency.

[0033] 2. For the bypass Roots pump provided by the present invention, its first one-way valve is convenient for assembly and maintenance, and the compression degree of its first spring can also be adjusted by adjusting the screwing length of the one-way valve bolts of each valve, thus conveniently controlling the opening pressure of the one-way valve. This not only makes the adjustment work simple, but also can be specifically set with different opening pressures according to different working conditions, enhancing the adaptability of the equipment.

[0034] 3. The bypass Roots pump provided by the present invention has a second check valve that can provide a direct pumping channel when the fore pump evacuates the vacuum and the Roots pump is not working, thereby accelerating the pumping efficiency of the entire system. When sharing the first channel 3 and the second channel 12 with the first check valve, the second check valve realizes a flow structure opposite to that of the first check valve, with a compact structure and no excessive occupied space. Moreover, by adjusting the position of the external thread sleeve 16 in the direct pumping threaded hole 18, the compression degree of the second spring 19 can be controlled, and ultimately the opening pressure of the second check valve can be adjusted, facilitating the control of the direct pumping opening pressure according to different working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0036] Figure 1 It is a right side view cross-sectional view showing the structure of an embodiment of the present invention;

[0037] Figure 2 It is Figure 1 a cross-sectional view taken along line A - A in

[0038] Figure 3 It is Figure 2 a partially enlarged view at position B in

[0039] Figure 4 It is a front view showing the structure of the plate body of an embodiment of the present invention;

[0040] Figure 5 It is a rear view showing the structure of the plate body of an embodiment of the present invention.

[0041] DESCRIPTION OF THE REFERENCE NUMERALS:

[0042] 1 - transverse channel, 2 - check valve bolt, 3 - first channel, 4 - housing main body, 5 - intake cavity, 6 - rotor, 7 - exhaust cavity, 8 - opening, 9 - bypass plate, 10 - cover plate, 11 - longitudinal channel, 12 - second channel, 13 - valve plate, 14 - rotor connection hole, 15 - plug, 16 - external thread sleeve, 17 - second steel ball, 18 - direct pumping threaded hole, 19 - second spring, 20 - stepped hole, 21 - first steel ball, 22 - first spring. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0045] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] This embodiment provides a bypass Roots pump.

[0048] In one embodiment, as Figure 1 shown, it includes: a pump housing and two rotors 6. The pump housing has a hollow inner cavity. The two rotors 6 mesh with each other and are rotatably arranged in the hollow inner cavity, thereby dividing the hollow inner cavity into an intake cavity 5 and an exhaust cavity 7. The pump housing is provided with a first channel 3 and a second channel 12. The first channel 3 communicates with one of the intake cavity 5 and the exhaust cavity 7, and the second channel 12 communicates with the other of the intake cavity 5 and the exhaust cavity 7. In Figure 1 this embodiment, the first channel 3 communicates with the intake cavity 5, and the second channel 12 communicates with the exhaust cavity 7. Obviously, the reverse setting is also possible. Two or more first one-way valves are arranged in parallel between the first channel 3 and the second channel 12. After the first one-way valve is opened, the flow direction of the gas passing through the first one-way valve is from the exhaust cavity 7 to the intake cavity 5. At least two of the first one-way valves have different opening pressures.

[0049] During the actual use of a Roots pump, the limit values of the air pressure increase caused by different situations will vary. For example, the air pressure increase caused by the gas flow surge of the fore pump is characterized by a small amplitude and a short maintenance time, while if the exhaust end pipeline ruptures and is connected to the atmosphere, the air pressure amplitude increase is high and the maintenance time is long. When the bypass Roots pump of this embodiment is working, no matter what causes the air pressure to increase slightly and reach the warning value, the first one-way valve with a lower pressure will be opened to play the bypass protection function. However, when the single bypass valve is opened, its flow rate is relatively small, thus preventing a large amount of the already extracted air flow from flowing back to the intake end, ensuring that the overall pumping efficiency of the system will not be significantly reduced. At this time, if the external air pressure increases slightly and for a short period, as the pressure difference decreases automatically or passively, the bypass function will be closed, and the pump will re-enter the normal working condition. If the situation is a relatively long-term and high amplitude increase, due to the continuity of the air pressure increase, as the air pressure increases, it will trigger the opening of the one-way valve with a higher pressure arranged in parallel. With the opening of the second bypass valve, the parallel valve cavity makes the flow rate of the entire device relatively larger, thereby quickly reducing the pressure difference between the two ends of the Roots pump until it is reduced to the point where the one-way valve with a higher opening pressure closes and only the one-way valve with a smaller opening pressure remains open. At this time, the flow rate decreases to weaken the negative impact of the bypass protection on reducing the pumping efficiency. Of course, this embodiment can set more first one-way valves with different pressure differences and flow gradients to adapt to different working conditions.

[0050] Based on the above-described embodiment, in a preferred embodiment, as Figure 1 shown, the pump housing includes: a housing main body 4 and a bypass plate 9. The bypass plate 9 is hermetically connected to the housing main body 4, thus enclosing the hollow inner cavity. The bypass plate 9 is arranged at the end of the rotor 6 and is rotatably connected to the rotor 6 through a rotor connection hole 14 or an equivalent boss. Both the first channel 3 and the second channel 12 are opened on the bypass plate 9.

[0051] Setting the bypass plate 9 that can be separated from the pump main body facilitates installation, debugging, maintenance, and repair. And setting the bypass plate 9 as a wall plate at the end of the rotor 6 compared to setting it on the circumferential side wall of the rotor 6 can keep its plate body straight, without the need to fit the circumference of the rotor 6. Therefore, the manufacturing of the bypass plate 9 can be made simple, and it is also convenient for the installation of the rotor 6.

[0052] Based on the above-described embodiment, in a preferred embodiment, as Figures 1 to 5 shown, the second channel 12 includes a longitudinal channel 11. The longitudinal channel 11 crosses the connection line of the axes of the two rotors 6, that is, Figure 2 the connection line of the axes of the two rotor connection holes 14 in

[0053] The bypass plate 9 arranged in this way shortens the distance between the first channel 3 and the second channel 12 through the longitudinal channel 11, thereby facilitating the setting of a miniaturized one-way valve between the two, reducing the related costs. The longitudinal channel 11 passes through the connection line of the axes of the two rotors 6, enabling the longitudinal channel 11 to shorten the distance to the first channel 3 with a relatively short length, so as to reduce the related processing amount. Therefore, the longitudinal channel 11 can preferably be located on the perpendicular bisector of the connection line of the axes of the two rotors 6. The longitudinal channel 11 communicates with the cavity where the rotor 6 is located through the opening 8, which ensures the integrity of the wall surface cooperating with the shaft end of the rotor 6 and ensures the normal air extraction function of the pump.

[0054] Based on the above-described embodiment, in a preferred embodiment, as Figures 1 to 5 shown, the second channel 12 further includes a transverse channel 1. The transverse channel 1 communicates with one end of the longitudinal channel 11 far away from the opening 8 and is parallel to the connection line of the axes of the two rotors 6. The first channel 3 is arranged in parallel with the transverse channel 1, and the first one-way valves are arranged side by side along the direction of the transverse channel 1.

[0055] Due to the limitation of the width of the longitudinal channel 11, it is not convenient to arrange a relatively large number of first one-way valves side by side. By arranging the transverse channel 1 at one end of the longitudinal channel 11 far away from the opening 8, that is, at one end close to the first channel 3, and arranging the first channel 3 in parallel with the transverse channel 1, the setting space of the one-way valve is thus widened, facilitating the reasonable layout among components. The transverse channel 1 is parallel to the connection line of the axes of the two rotors 6, which can maximize the use of the maximum side length of the flat and long cross-section formed by the two rotors 6 of the roots pump, facilitating the installation and debugging of the side-by-side arranged one-way valves.

[0056] Based on the above-described embodiment, in a preferred embodiment, as Figures 1 to 5 shown, the bypass plate 9 includes: a cover plate 10 and a valve plate 13. One side of the valve plate 13 is hermetically connected to the shell main body 4; a first slot is dug on the side of the valve plate 13 facing the shell main body 4, thereby forming the first channel 3; a second slot is dug on the side of the valve plate 13 facing away from the shell main body 4 and is hermetically connected to the cover plate 10, thereby forming the second channel 12.

[0057] This structure of forming the corresponding channels by slots is convenient for processing. Especially for non-linear channels, such as T-shaped or L-shaped channels, the corresponding channels can be milled on the plate body, rather than being formed by the conventional method of drilling and then plugging, which can simplify the processing process.

[0058] Based on the above-described embodiment, in a preferred embodiment, as Figures 1 to 5 shown, the first channel 3 is located between the transverse channel 1 and the side of the bypass plate 9. This can reduce the elongation distance of the longitudinal channel 11, reduce the processing cost, and the structural layout is more reasonable.

[0059] Based on the above-described embodiments, in a preferred embodiment, as Figure 3 shown, the first one-way valve includes: a stepped hole 20, a first steel ball 21, a one-way valve bolt 2, and a first spring 22. The stepped hole 20 is provided between the first passage 3 and the second passage 12. The first steel ball 21 is placed in the large hole of the stepped hole 20. The diameter of the first steel ball 21 is greater than the diameter of the small hole of the stepped hole 20 and less than the diameter of the large hole of the stepped hole 20. The one-way valve bolt 2 is threadedly connected to the bypass plate 9 through a threaded hole provided between the first passage 3 and the side of the bypass plate 9. The first spring 22 is located between the first steel ball 21 and the one-way valve bolt 2; the head end of the one-way valve bolt 2 presses the first spring 22 to make the first steel ball 21 abut against the orifice of the small hole of the stepped hole 20.

[0060] The first one-way valve with such a structure is convenient for assembly, maintenance, and repair. Moreover, the compression degree of the first spring 22 can be adjusted by adjusting the screwing-in length of the one-way valve bolt 2 of each valve, so as to conveniently control the opening pressure of the one-way valve. This not only makes the adjustment work simple but also can be targeted to set different opening pressures according to different working conditions. Of course, in this embodiment, in addition to setting the opening pressure by adjusting the screwing-in length of the one-way valve bolt 2, different opening pressures can also be achieved by fully screwing in the one-way valve bolts 2 with different rod lengths, or by using the same specification bolts but matching the first springs 22 with different lengths or elastic coefficients to achieve different opening pressures.

[0061] Based on the above-described embodiments, in a preferred embodiment, as Figures 1 to 5 shown, a second one-way valve is provided between the first passage 3 and the second passage 12. The flow direction of the second one-way valve is from the intake cavity 5 to the exhaust cavity 7. Adding the second one-way valve can provide a direct pumping channel when the front-stage pump is evacuating and the roots pump is not working, thereby improving the pumping efficiency of the entire system.

[0062] Based on the above-described embodiments, in a preferred embodiment, as Figure 3 shown, the second one-way valve includes: a direct pumping threaded hole 18, an external threaded sleeve 16, a second steel ball 17, and a second spring 19. The direct pumping threaded hole 18 is provided between the first passage 3 and the second passage 12. The external threaded sleeve 16 has a central through hole, and the outer surface of the external threaded sleeve 16 is threadedly connected to the direct pumping threaded hole 18. The diameter of the second steel ball 17 is greater than the diameter of the central through hole and abuts against the edge of the central through hole. A spring hole is provided between the direct pumping threaded hole 18 and the second passage 12. After the second spring 19 passes through the spring hole, one end of the second spring 19 is fixed on the side wall of the second passage 12, so that the second spring 19 is located between the second passage 12 and the second steel ball 17. At the same time, the diameter of the second steel ball 17 is not less than the diameter of the spring hole. The external threaded sleeve 16 compresses the second steel ball 17 to make the second spring 19 in a compressed state.

[0063] In the case where the second one-way valve of this structure shares the first channel 3 and the second channel 12 with the first one-way valve, a flow structure opposite to that of the first one-way valve is realized. The gas sequentially passes through the first channel 3, the external thread sleeve 16 to reach the second steel ball 17, and after pushing open the second steel ball 17, it flows into the second channel 12 through the spring hole. Its structure is compact and does not occupy too much extra space. And it controls the compression degree of the second spring 19 by adjusting the position of the external thread sleeve 16 in the direct extraction thread hole 18, and finally can adjust the opening pressure of the second one-way valve, which is convenient to control the direct extraction opening pressure according to different working conditions.

[0064] Based on the above embodiment, in a preferred embodiment, as Figure 3 shown, an assembly thread hole is provided between the first channel 3 and the side of the bypass plate 9; the diameter of the assembly thread hole is larger than the outer diameter of the external thread sleeve 16 and faces the direct extraction thread hole 18; an internal hexagonal counterbore is provided at one end of the external thread sleeve 16 close to the assembly thread hole, and a plug 15 is sealingly connected to the assembly thread hole.

[0065] The second one-way valve of this structure can conveniently install the core components of the second one-way valve through the assembly thread hole, and through the internal hexagonal counterbore of the external thread sleeve 16, after opening the plug 15, it is convenient to adjust the compression amount of the second spring 19 with an internal hexagonal wrench to adjust the direct extraction pressure for the on-site working conditions.

[0066] Obviously, the above embodiments are only examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made on the basis of the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A bypass Roots pump, characterized in that, Comprising: A pump housing having a hollow inner cavity; Two rotors (6), which mesh with each other and are rotatably arranged in the hollow inner cavity, dividing the hollow inner cavity into an air inlet cavity (5) and an air exhaust cavity (7); The pump housing is provided with a first channel (3) and a second channel (12); the first channel (3) is communicated with one of the air inlet cavity (5) and the air exhaust cavity (7), and the second channel (12) is communicated with the other of the air inlet cavity (5) and the air exhaust cavity (7); A plurality of first one-way valves are arranged in parallel between the first channel (3) and the second channel (12); after the first one-way valve is opened, the flow direction of the gas passing through the first one-way valve is from the air exhaust cavity (7) to the air inlet cavity (5); at least two of the first one-way valves have different opening pressures; The pump housing includes: A housing main body (4); A bypass plate (9), which is hermetically connected to the housing main body (4) to enclose the hollow inner cavity; the bypass plate (9) is arranged at the end of the rotor (6) and is rotatably connected to the rotor (6); both the first channel (3) and the second channel (12) are arranged on the bypass plate (9), and the first channel (3) is located between the transverse channel (1) and the side of the bypass plate (9); The second channel (12) includes a longitudinal channel (11) and a transverse channel (1), the longitudinal channel (11) crosses the connecting line of the axes of the two rotors (6), the first one-way valve is arranged at one end of the longitudinal channel (11), the other end of the longitudinal channel (11) is communicated with the air inlet cavity (5) or the air exhaust cavity (7) through an opening (8), the transverse channel (1) is communicated with the end of the longitudinal channel (11) far away from the opening (8) and is parallel to the connecting line of the axes of the two rotors (6), the first channel (3) is arranged in parallel with the transverse channel (1), and the first one-way valves are arranged side by side along the direction of the transverse channel (1); The bypass plate (9) includes: A cover plate (10); A valve plate (13); one side of the valve plate (13) is hermetically connected to the housing main body (4); the valve plate (13) is provided with a first groove on the side facing the housing main body (4) to form the first channel (3); the valve plate (13) is provided with a second groove on the side facing away from the housing main body (4) and is hermetically connected to the cover plate (10) to form the second channel (12).

2. The bypass Roots pump according to claim 1, characterized in that, The first one-way valve includes: A stepped hole (20), which is arranged between the first channel (3) and the second channel (12); A first steel ball (21), which is placed in the large hole of the stepped hole (20), and the diameter of the first steel ball (21) is larger than the diameter of the small hole of the stepped hole (20); A one-way valve bolt (2), which is threadedly connected to the bypass plate (9) through a threaded hole arranged between the first channel (3) and the side of the bypass plate (9); A first spring (22), which is located between the first steel ball (21) and the one-way valve bolt (2); the head end of the one-way valve bolt (2) presses the first spring (22) to make the first steel ball (21) abut against the orifice of the small hole of the stepped hole (20).

3. The bypass Roots pump according to claim 1 or 2, characterized in that, A second one-way valve is arranged between the first channel (3) and the second channel (12), and the flow direction of the second one-way valve is from the air inlet cavity (5) to the air exhaust cavity (7).

4. The bypass Roots pump according to claim 3, characterized in that, The second one-way valve includes: A direct-drawing threaded hole (18) is provided between the first channel (3) and the second channel (12); An external-thread sleeve (16) has a central through-hole and is threadedly connected to the direct-drawing threaded hole (18); A second steel ball (17) has a diameter larger than the diameter of the central through-hole and abuts against the edge of the central through-hole; A second spring (19) is located between the second channel (12) and the second steel ball (17), and the external-thread sleeve (16) compresses the second spring (19) by pressing the second steel ball (17).

5. The bypass Roots pump according to claim 4, characterized in that, An assembly threaded hole is provided between the first channel (3) and the side of the bypass plate (9); the diameter of the assembly threaded hole is larger than the outer diameter of the external-thread sleeve (16) and faces the direct-drawing threaded hole (18); the external-thread sleeve (16) is provided with a countersunk hexagon socket at one end close to the assembly threaded hole, and a plug (15) is sealingly connected to the assembly threaded hole.

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