CN214698321U - Variable pitch screw host, all-in-one machine, air compressor, vacuum pump and expansion machine - Google Patents

Abstract

The utility model discloses a variable pitch screw rod host computer, all-in-one, air compressor machine, vacuum pump, expander, variable pitch screw rod host computer include one-level rotor set and second grade rotor set, one-level rotor set receive the drive of outside driving source and operate, one-level rotor set to the transmission of second grade rotor set, the negative and positive rotors of one-level rotor set and/or the negative and positive rotors of second grade rotor set are the variable pitch screw rod. The volume of the medium cavity of the first-stage rotor set and/or the volume of the medium cavity of the second-stage rotor set are gradually reduced or increased by adopting the variable-pitch screw, the female rotor of the first-stage rotor set and/or the female rotor of the second-stage rotor set have the process of internal compression or internal expansion in the process of mutual meshing, the compression ratio or the expansion ratio can be improved, the pressurization or expansion process of a gas medium can be stable, the compression or expansion power consumption is reduced, and the safety and reliability of a host machine are improved.

Description

Variable pitch screw host, all-in-one machine, air compressor, vacuum pump and expansion machine

Technical Field

The utility model relates to a technical field of the compression or the inflation of air, more exactly relate to a variable pitch screw rod host computer, all-in-one, air compressor machine, vacuum pump, expander.

Background

In the field of rotary air compressors or expanders, a double-screw rotor is usually adopted to form a periodically-changed working cavity volume in the rotary motion, so that the processes of entering, compressing/expanding and discharging a working medium are realized, the air compressor converts the mechanical energy of a power system into gas pressure energy, and the expander converts the internal energy of the working medium into mechanical energy.

At present, in the industry of air compressors, in order to increase the compression capacity, a two-stage screw main machine is being more and more widely applied, the two-stage screw main machine is provided with a two-stage rotor set, the two-stage screw main machine comprises a set of low-pressure rotor set and a set of high-pressure rotor set which are horizontally distributed, the low-pressure rotor set and the high-pressure rotor set are horizontally distributed, gas enters the high-pressure rotor set after being subjected to one-stage compression by the low-pressure rotor set, and is discharged after being subjected to two-stage compression by the high-pressure rotor set. Because the gas volume is reduced after the gas is compressed by the low-pressure rotor set in one stage, the size of the rotor in the high-pressure rotor set is usually smaller than that of the rotor in the low-pressure rotor set; meanwhile, in order to satisfy the air quantity relation, the size of the main engine on the low-pressure rotor set side is larger than that of the main engine on the high-pressure rotor set side.

In the field of expansion machines, in order to realize a large expansion ratio and increase the output power of the expansion machine, a two-stage screw main machine is also often adopted, the two-stage screw main machine comprises a first-stage rotor set and a second-stage rotor set which are horizontally distributed, gas enters the second-stage rotor set after being subjected to first-stage expansion by the first-stage rotor set, and then is subjected to second-stage expansion by the second-stage rotor set. Because the volume of the gas is increased after the gas is expanded by the first-stage rotor set, the size of the rotor of the second-stage rotor set is generally larger than that of the rotor of the first-stage rotor set; meanwhile, in order to satisfy the air quantity relation, the size of the main engine on the side of the primary rotor set is smaller than that of the main engine on the side of the secondary rotor set.

The larger size of the main machine has the defect of insufficient space utilization of the main machine, and if a larger compression ratio or expansion ratio can be realized in the main machine with the same size, the influence caused by the defect can be compensated.

SUMMERY OF THE UTILITY MODEL

The to-be-solved technical problem of the utility model is to provide a variable pitch screw rod host computer, can realize bigger compression ratio or expansion ratio in the host computer of the same size.

The technical solution of the utility model is that, including one-level rotor group and second grade rotor group, the one-level rotor group be operated by the drive of external drive source, the one-level rotor group transmit to the second grade rotor group, the one-level rotor group includes intermeshing's one-level male rotor and one-level female rotor, the second grade rotor group includes intermeshing's second grade male rotor and second grade female rotor, the one-level male rotor and one-level female rotor be the variable pitch screw rod, second grade male rotor and second grade female rotor be the uniform pitch screw rod or the variable pitch screw rod; or the first-stage male rotor and the first-stage female rotor are both equal-pitch screws, and the second-stage male rotor and the second-stage female rotor are both variable-pitch screws.

Compared with the prior art, the utility model discloses a variable pitch screw rod host computer has following advantage: the male and female rotors of the primary rotor set and/or the male and female rotors of the secondary rotor set are variable-pitch screws, the volumes of the medium cavities of the primary rotor set and/or the secondary rotor set are gradually reduced or increased, and the male and female rotors of the primary rotor set and/or the male and female rotors of the secondary rotor set have an internal compression or internal expansion process in the mutual meshing process, so that the compression ratio or expansion ratio can be improved, the pressurization or expansion process of a gas medium can be stable, the compression or expansion power consumption is reduced, and the safety and reliability of a host machine are improved; the driving source of rotor group can be external, makes the utility model discloses a variable pitch screw rod host computer can adapt to multiple application scene.

Preferably, the first-stage male rotor and the first-stage female rotor are variable-pitch screws and are formed by connecting a plurality of sections of screws with different pitches end to end. By adopting the structure, the first-stage male rotor and the first-stage female rotor are both multi-section variable-pitch screws.

Preferably, the first-stage male rotor and the first-stage female rotor are variable-pitch screws and are composed of screws with gradually-changed pitches. By adopting the structure, the first-stage male rotor and the first-stage female rotor are both of a gradually-changed variable-pitch screw.

Preferably, the second-stage male rotor and the second-stage female rotor are variable-pitch screws and are formed by connecting a plurality of sections of screws with different pitches end to end. By adopting the structure, the secondary male rotor and the secondary female rotor are both multi-section variable-pitch screws.

Preferably, the secondary male rotor and the secondary female rotor are both variable-pitch screws and are both composed of screws with gradually-changed pitches. By adopting the structure, the secondary male rotor and the secondary female rotor are both of a gradually-changed variable-pitch screw.

Preferably, one end of the first-stage male rotor is used for being connected with an external driving source, a transmission part is arranged between the other end of the first-stage male rotor and the second-stage male rotor, the external driving source drives the first-stage male rotor to perform transmission, the first-stage male rotor performs meshing transmission on the first-stage female rotor, the first-stage male rotor performs transmission on the second-stage male rotor through the transmission part, and the second-stage male rotor performs meshing transmission on the second-stage female rotor. By adopting the structure, the structure is simple, and the volume of the main machine can be reduced by adopting meshing transmission between the male rotor and the female rotor.

The to-be-solved technical problem of the utility model is to provide a variable pitch screw rod all-in-one can realize bigger compression ratio or expansion ratio in the host computer of the same size.

The technical solution of the utility model is, including the motor and as above the pitch-variable screw rod host computer, the one end of one-level male rotor is connected with the motor and receives the drive of motor and the operation, and one-level rotor group and second grade rotor group level are established ties.

Compared with the prior art, the utility model discloses a variable pitch screw rod all-in-one has following advantage: the male and female rotors of the primary rotor set and/or the male and female rotors of the secondary rotor set are variable-pitch screws, the volumes of the medium cavities of the primary rotor set and/or the secondary rotor set are gradually reduced or increased, and the male and female rotors of the primary rotor set and/or the male and female rotors of the secondary rotor set have an internal compression or internal expansion process in the mutual meshing process, so that the compression ratio or expansion ratio can be improved, the pressurization or expansion process of a gas medium can be stable, the compression or expansion power consumption is reduced, and the safety and reliability of a host machine are improved; the motor is integrated with the variable-pitch screw main machine, so that an external driving source is avoided, the running reliability of the primary rotor set and the secondary rotor set is ensured, and the volume of the whole machine can be reduced; the first-stage rotor set and the second-stage rotor set are horizontally connected in series, so that the gas circulation efficiency can be improved, and the pressure loss of gas can be reduced.

The to-be-solved technical problem of the utility model is to provide an air compressor machine can realize bigger compression ratio in the host computer of the same size, improves compression efficiency.

The technical solution of the utility model is, provide an air compressor machine, including induction port, gas vent and as above variable pitch screw rod host computer, the induction port set up the induction end of organizing at the one-level rotor, the exhaust end of organizing of one-level rotor and the induction end intercommunication of second grade rotor group, the gas vent set up the exhaust end of organizing at the second grade rotor, the size of one-level male rotor and one-level female rotor will be greater than the size of second grade male rotor and second grade female rotor.

Compared with the prior art, the utility model discloses an air compressor machine has following advantage: the male and female rotors of the primary rotor set and/or the male and female rotors of the secondary rotor set are variable-pitch screws, the volumes of the medium cavities of the primary rotor set and/or the secondary rotor set are gradually reduced, and the male and female rotors of the primary rotor set and/or the male and female rotors of the secondary rotor set have an internal compression process in the mutual meshing process, so that the compression ratio can be improved, the pressurization process of a gas medium can be stable, the power consumption of an air compressor is reduced, and the safety and reliability of a host machine are improved.

The to-be-solved technical problem of the utility model is to provide a vacuum pump, can realize bigger compression ratio in the host computer of the same size, improve vacuum extraction efficiency.

The technical solution of the utility model is, provide the vacuum pump, including induction port, gas vent and as above variable pitch screw rod host computer, the induction port set up the induction end at one-level rotor group, the exhaust end of one-level rotor group and the induction end intercommunication of second grade rotor group, the gas vent set up the exhaust end at second grade rotor group, the size of one-level male rotor and one-level female rotor will be greater than the size of second grade male rotor and second grade female rotor.

Compared with the prior art, the utility model discloses a vacuum pump has following advantage: the male and female rotors of the primary rotor set and/or the male and female rotors of the secondary rotor set are variable-pitch screws, the volumes of the medium cavities of the primary rotor set and/or the secondary rotor set are gradually reduced, and the male and female rotors of the primary rotor set and/or the male and female rotors of the secondary rotor set have an internal compression process in the process of mutual meshing, so that the compression ratio can be improved, the vacuum extraction efficiency of the vacuum pump can be improved, the vacuum extraction process of the vacuum pump can be stable, the power consumption of the vacuum pump for pumping is reduced, and the safety and reliability of a host machine are improved.

The to-be-solved technical problem of the utility model is to provide an expander, can realize bigger expansion ratio in the host computer of the same size.

The technical solution of the utility model is, provide an expander, including induction port, gas vent and as above variable pitch screw rod host computer, the induction port set up the induction end of organizing at the one-level rotor, the exhaust end of organizing of one-level rotor and the induction end intercommunication of second grade rotor group, the gas vent set up the exhaust end of organizing at the second grade rotor, the size of one-level male rotor and one-level female rotor will be less than the size of second grade male rotor and second grade female rotor.

Compared with the prior art, the utility model discloses an expander has following advantage: the male and female rotors of the primary rotor set and/or the male and female rotors of the secondary rotor set are variable-pitch screws, the volumes of the medium cavities of the primary rotor set and/or the secondary rotor set are gradually increased, and the male and female rotors of the primary rotor set and/or the male and female rotors of the secondary rotor set have an internal expansion process in the mutual meshing process, so that the expansion ratio can be improved, the working efficiency of the expansion machine is improved, the expansion process of a gas medium can be stable, the power consumption of the expansion machine is reduced, and the safety and reliability of a host machine are improved.

Drawings

Fig. 1 is a schematic structural view of the variable pitch screw host of the present invention.

Fig. 2 is the structure schematic diagram of the variable pitch screw rod all-in-one machine of the utility model.

Fig. 3 is the schematic structural diagram of the variable pitch screw of the multi-stage type for the middle-stage male rotor and the first-stage female rotor.

As shown in the figure: 1. the rotor comprises a first-stage male rotor, a second-stage female rotor, a first-stage male rotor, a second-stage female rotor, a driving gear, a second-stage driven gear and a motor, wherein the first-stage male rotor is 2, the first-stage female rotor is 3, the second-stage male rotor is 4, the second-stage female rotor is 5, the driving gear is 6, the driven gear is 7.

Detailed Description

For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that the detailed description is merely illustrative of exemplary embodiments of the present application and does not limit the scope of the present application in any way. Like reference numerals refer to like elements throughout the specification.

In the drawings, the thickness, size, and shape of an object have been slightly exaggerated for convenience of explanation. The figures are purely diagrammatic and not drawn to scale.

It will be further understood that the terms "comprises," "comprising," "includes," "including," and/or "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Further, when a statement such as "… at least one" appears after the list of listed features, the entire listed feature is modified rather than modifying individual elements in the list.

Example 1:

as shown in fig. 2, the variable pitch screw integrated machine of the present invention comprises a motor 7 and a variable pitch screw host; the utility model discloses a variable pitch screw rod host computer is as shown in figure 1, including one-level rotor set and second grade rotor set, the one-level rotor set includes intermeshing's one-level male rotor 1 and one-level female rotor 2, and one-level male rotor 1 and one-level female rotor 2 are variable pitch screw rod and axis and are parallel to each other, second grade rotor set includes intermeshing's second grade male rotor 3 and second grade female rotor 4, and second grade male rotor 3 and second grade female rotor 4 also are variable pitch screw rod and axis and are parallel to each other. One end of one-level male rotor 1 is used for being connected with external drive source, and external drive source is motor 7 in this embodiment, and the other end of one-level male rotor 1 is connected with driving gear 5, and the one end of second grade male rotor 3 is connected with driven gear 6, and meshing transmission between driving gear 5 and the driven gear 6, one-level rotor group and second grade rotor group level are established ties. The motor 7 drives the first-stage male rotor 1 to rotate, the first-stage male rotor 1 is in meshing transmission with the first-stage female rotor 2, the first-stage male rotor 1 is in transmission with the second-stage male rotor 3 through the meshed driving gear 5 and the driven gear 6, and the second-stage male rotor 3 is in meshing transmission with the second-stage female rotor 4. The primary male rotor 1 can also drive the secondary male rotor 3 through a drive belt. The first-stage male rotor 1 and the first-stage female rotor 2 can be multi-section variable-pitch screws, namely, the screws with different pitches are connected end to form the variable-pitch rotor, as shown in fig. 3; the first-stage male rotor 1 and the first-stage female rotor 2 may be a tapered variable-pitch screw, that is, a screw whose pitch changes gradually. Similarly, the secondary male rotor 3 and the secondary female rotor 4 may be a multi-stage variable pitch screw or a progressive variable pitch screw.

Example 2:

the difference between this embodiment and embodiment 1 is that the first-stage male rotor 1 and the first-stage female rotor 2 are both equal-pitch screws, and the second-stage male rotor 3 and the second-stage female rotor 4 are multi-stage variable-pitch screws or gradual variable-pitch screws.

Example 3:

the present embodiment is different from embodiment 1 in that the first-stage male rotor 1 and the first-stage female rotor 2 are multi-stage variable pitch screws or gradual variable pitch screws, and the second-stage male rotor 3 and the second-stage female rotor 4 are constant pitch screws.

Example 4:

the utility model discloses an air compressor machine includes the casing, be provided with one-level compression chamber and second grade compression chamber in the casing and like any one variable pitch screw rod host computer in embodiment 1 to embodiment 3, the exhaust end in one-level compression chamber and the inspiratory limb level intercommunication in second grade compression chamber, one-level male rotor 1 and one-level female rotor 2 set up in one-level compression intracavity, second grade male rotor 3 and second grade female rotor 4 set up in the second grade compression intracavity, one end that one-level male rotor 1 is located one-level compression chamber exhaust end is connected with driving gear 5, the one end that second grade male rotor 3 is located second grade compression chamber inspiratory limb is connected with driven gear 6, meshing transmission between driving gear 5 and the driven gear 6.

The first-stage male rotor 1 and the first-stage female rotor 2 are variable-pitch screws with gradually reduced pitches, and the second-stage male rotor 3 and the second-stage female rotor 4 are equal-pitch screws; or the first-stage male rotor 1 and the first-stage female rotor 2 are equal-pitch screws, and the second-stage male rotor 3 and the second-stage female rotor 4 are variable-pitch screws with gradually reduced pitches; or the first-stage male rotor 1 and the first-stage female rotor 2, and the second-stage male rotor 3 and the second-stage female rotor 4 are variable-pitch screws with gradually reduced pitches. The suction end corresponding to the first-stage compression cavity on the shell is provided with an air suction port, the exhaust end corresponding to the second-stage compression cavity on the shell is provided with an air exhaust port, the sizes of the first-stage male rotor 1 and the first-stage female rotor 2 are larger than the sizes of the second-stage male rotor 3 and the second-stage female rotor 4, and one end, located at the suction end of the first-stage compression cavity, of the first-stage male rotor 1 is connected with a motor 7. The motor 7 drives the first-stage male rotor 1 to rotate, the first-stage male rotor 1 is in meshing transmission with the first-stage female rotor 2, the first-stage male rotor 1 is in transmission with the second-stage male rotor 3 through the meshed driving gear 5 and the driven gear 6, and the second-stage male rotor 3 is in meshing transmission with the second-stage female rotor 4.

Example 5:

the utility model discloses a vacuum pump includes the casing, be provided with one-level air exhaust chamber and second grade air exhaust chamber and like any one variable pitch screw rod host computer in embodiment 1 to embodiment 3 in the casing, the exhaust end in one-level air exhaust chamber and the inspiratory limb level intercommunication in second grade air exhaust chamber, one-level male rotor 1 and the setting of one-level female rotor 2 are in the one-level air exhaust intracavity, second grade male rotor 3 and the setting of second grade female rotor 4 are in the second grade is bled, one-level male rotor 1 is located the one-level air exhaust end of air exhaust chamber and is connected with driving gear 5, the one end that second grade male rotor 3 is located the second grade air exhaust chamber inspiratory limb is connected with driven gear 6, meshing transmission between driving gear 5 and the driven gear 6.

The first-stage male rotor 1 and the first-stage female rotor 2 are variable-pitch screws with gradually reduced pitches, and the second-stage male rotor 3 and the second-stage female rotor 4 are equal-pitch screws; or the first-stage male rotor 1 and the first-stage female rotor 2 are equal-pitch screws, and the second-stage male rotor 3 and the second-stage female rotor 4 are variable-pitch screws with gradually reduced pitches; or the first-stage male rotor 1 and the first-stage female rotor 2, and the second-stage male rotor 3 and the second-stage female rotor 4 are variable-pitch screws with gradually reduced pitches. The suction end corresponding to the first-stage air suction cavity on the shell is provided with an air suction port, the exhaust end corresponding to the second-stage air suction cavity on the shell is provided with an air exhaust port, the sizes of the first-stage male rotor 1 and the first-stage female rotor 2 are larger than the sizes of the second-stage male rotor 3 and the second-stage female rotor 4, and one end, located at the suction end of the first-stage air suction cavity, of the first-stage male rotor 1 is connected with a motor 7. The motor 7 drives the first-stage male rotor 1 to rotate, the first-stage male rotor 1 is in meshing transmission with the first-stage female rotor 2, the first-stage male rotor 1 is in transmission with the second-stage male rotor 3 through the meshed driving gear 5 and the driven gear 6, and the second-stage male rotor 3 is in meshing transmission with the second-stage female rotor 4.

Example 6:

the utility model discloses an expander includes the casing, be provided with one-level expansion chamber and second grade expansion chamber in the casing and as in embodiment 1 to embodiment 3 arbitrary variable pitch screw rod host computer, the exhaust end in one-level expansion chamber and the inspiratory limb level intercommunication in second grade expansion chamber, one-level male rotor 1 and one-level female rotor 2 set up in one-level expansion chamber, second grade male rotor 3 and second grade female rotor 4 set up in the second grade inflation, one end that one-level male rotor 1 is located one-level expansion chamber exhaust end is connected with driving gear 5, the one end that second grade male rotor 3 is located second grade expansion chamber inspiratory limb is connected with driven gear 6, meshing transmission between driving gear 5 and the driven gear 6.

The first-stage male rotor 1 and the first-stage female rotor 2 are variable-pitch screws with gradually increasing pitches, and the second-stage male rotor 3 and the second-stage female rotor 4 are constant-pitch screws; or the first-stage male rotor 1 and the first-stage female rotor 2 are equal-pitch screws, and the second-stage male rotor 3 and the second-stage female rotor 4 are variable-pitch screws with gradually increasing pitches; or the first-stage male rotor 1 and the first-stage female rotor 2, and the second-stage male rotor 3 and the second-stage female rotor 4 are variable-pitch screws with gradually increasing pitches. The suction end that corresponds one-level expansion chamber on the casing sets up the induction port, the exhaust end that corresponds second grade expansion chamber on the casing sets up the gas vent, the size of one-level male rotor 1 and one-level female rotor 2 will be less than the size of second grade male rotor 3 and second grade female rotor 4, one end that one-level male rotor 1 is located one-level expansion chamber suction end is connected with motor 7, motor 7 drive one-level male rotor 1 rotates, one-level male rotor 1 meshes the transmission to one-level female rotor 2, one-level male rotor 1 passes through engaged driving gear 5 and driven gear 6 to the transmission of second grade male rotor 3, second grade male rotor 3 meshes the transmission to second grade female rotor 4.

Also can be that the one end that second grade positive rotor 3 is located second grade expansion chamber exhaust end is connected with motor 7, the one end that second grade positive rotor 3 is located second grade expansion chamber end of breathing in is connected with driving gear 5, the one end that one-level positive rotor 1 is located first grade expansion chamber exhaust end is connected with driven gear 6, meshing transmission between driving gear 5 and the driven gear 6, motor 7 drive second grade positive rotor 3 rotates, second grade positive rotor 3 is to the transmission of 4 meshes of second grade negative rotor, second grade positive rotor 3 is through the transmission of meshing driving gear 5 and driven gear 6 to one-level positive rotor 1 transmission, one-level positive rotor 1 is to the transmission of 2 meshes of one-level negative rotor. The transmission from the small-sized first-stage male rotor 1 to the large-sized second-stage male rotor 3 is avoided, and the safety and reliability of the main machine are improved.

The above are only specific embodiments of the present invention, and are not intended to limit the scope of the present invention; the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and equivalent arrangements as is within the spirit and scope of the present invention.

Claims (10)

1. A variable pitch screw host comprises a primary rotor set and a secondary rotor set, wherein the primary rotor set is driven by an external driving source to run, and the primary rotor set transmits to the secondary rotor set; or the first-stage male rotor and the first-stage female rotor are both equal-pitch screws, and the second-stage male rotor and the second-stage female rotor are both variable-pitch screws.

2. The variable pitch screw host machine of claim 1, wherein the primary male rotor and the primary female rotor are variable pitch screws and are formed by connecting a plurality of sections of screws with different pitches end to end.

3. The variable pitch screw host of claim 1, wherein the primary male rotor and the primary female rotor are variable pitch screws and are each comprised of screws having gradually changing pitches.

4. The variable pitch screw host machine of claim 1, wherein the secondary male rotor and the secondary female rotor are variable pitch screws and are formed by connecting a plurality of sections of screws with different pitches end to end.

5. The variable pitch screw host of claim 1, wherein the secondary male rotor and the secondary female rotor are variable pitch screws and are each comprised of screws having gradually changing pitches.

6. The variable pitch screw host machine according to any one of claims 1 to 5, wherein one end of the primary male rotor is adapted to be connected to an external driving source, a transmission member is provided between the other end of the primary male rotor and the secondary male rotor, the external driving source drives the primary male rotor to rotate, the primary male rotor is in meshing transmission with the primary female rotor, the primary male rotor is in transmission with the secondary male rotor through the transmission member, and the secondary male rotor is in meshing transmission with the secondary female rotor.

7. A variable pitch screw all-in-one machine is characterized by comprising a motor and a variable pitch screw main machine according to claim 6, wherein one end of a primary male rotor is connected with the motor and driven by the motor to operate, and a primary rotor set and a secondary rotor set are horizontally connected in series.

8. An air compressor, characterized in that, including the suction port, the exhaust port and according to claim 6 said variable pitch screw host computer, said suction port is set up in the suction end of the first order rotor group, the exhaust end of the first order rotor group communicates with suction end of the second order rotor group, said exhaust port is set up in the exhaust end of the second order rotor group, the size of the first order male rotor and first order female rotor should be greater than the size of the second order male rotor and second order female rotor.

9. A vacuum pump, characterized by comprising a suction port, an exhaust port and a variable pitch screw main unit according to claim 6, wherein the suction port is arranged at the suction end of the primary rotor set, the exhaust end of the primary rotor set is communicated with the suction end of the secondary rotor set, the exhaust port is arranged at the exhaust end of the secondary rotor set, and the size of the primary male rotor and the size of the primary female rotor are larger than that of the secondary male rotor and the secondary female rotor.

10. An expander comprising a suction port provided at a suction end of a primary rotor set, a discharge port communicating with a suction end of a secondary rotor set, and a variable pitch screw main unit according to claim 6, wherein the size of the primary male rotor and the primary female rotor is smaller than that of the secondary male rotor and the secondary female rotor.

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