Interstage plate for vacuum pump

Abstract

An interstage plate system comprising a first plate portion having a first recess on a first mating surface and a second plate portion having a second recess on a second mating surface, wherein the first plate portion and the second plate portion are joined together to form an interstage plate for a vacuum pump, the first mating surface and the second mating surface are in contact, the first recess and the second recess are opposing continuous recesses, and together they form an opening that penetrates the interstage plate.

Description

Technical Field

[0001] The present invention relates to an interstage plate system for forming an interstage plate for a vacuum pump, a rotor assembly for a vacuum, and a vacuum pump. The present invention relates to a method of assembling a rotor assembly and a vacuum pump.

Background Art

[0002] Vacuum pumps including a plurality of pump stages are known. Also known are composite vacuum pumps having a plurality of stages of different respective pump types. For example, a Roots screw type composite vacuum pump can include a first pump stage that houses meshing Roots rotors in fluid communication with each other and a second pump stage that houses meshing screw rotors.

Summary of the Invention

Means for Solving the Problems

[0003] In one aspect, an interstage plate system is provided that includes a first plate portion including a first recess on a first mating surface and a second plate portion including a second recess on a second mating surface. The first plate portion and the second plate portion are joined together to form an interstage plate for a vacuum pump, the first mating surface and the second mating surface are in contact, and the first recess and the second recess are opposing continuous recesses configured to together form an opening that passes through the interstage plate.

[0004] The first plate portion can further include a third recess on the first mating surface. The second plate portion can further include a fourth recess on the second mating surface. When the first plate portion and the second plate portion are joined together to form an interstage plate, the third recess and the fourth recess are opposing continuous recesses and can be further configured to together form a further opening that passes through the interstage plate.

[0005] The second plate portion may have a fifth recess, the fifth recess may be formed on a surface of the second plate portion other than the second mating surface. For example, the fifth recess may be formed on the surface of the second plate portion opposite to the second mating surface.

[0006] In a further embodiment, a rotor assembly for a vacuum pump is provided. The rotor assembly comprises an interstage plate formed by the interstage plate system of the above embodiment, a first rotor, a second rotor, and a first shaft. The first rotor and the second rotor are fixed to the first shaft in a coaxial alignment. The first shaft passes through openings in the interstage plate formed by the first and second recesses. The interstage plate is positioned between the first rotor and the second rotor.

[0007] The first rotor can be a Roots rotor. The second rotor can be a screw rotor.

[0008] The rotor assembly may further comprise a third rotor, a fourth rotor, and a second shaft. The interstage plate may have further openings through which it passes, the openings of which may be formed by a third recess and a fourth recess. The third and fourth rotors may be fixed in coaxial alignment with the second shaft. The second shaft may pass through further openings in the interstage plate. The interstage plate may be positioned between the third and fourth rotors. The second shaft may be substantially parallel to the first shaft.

[0009] The third rotor can be a Roots rotor. The fourth rotor can be a screw rotor. The first and third rotors can mesh together. The second and fourth rotors can mesh together.

[0010] In a further embodiment, a vacuum pump is provided comprising a stator having a pump chamber and a rotor assembly as in any of the above embodiments. The rotor assembly is at least partially located within the pump chamber.

[0011] The stator may include a plate seat formed from one or more walls of the pump chamber. The plate seat may be formed between the first and second pump stages of the vacuum pump. An interstage plate can engage with the plate seat. The interstage plate can be fixedly attached to the plate seat.

[0012] The interstage plates can be formed from the same material as the stator.

[0013] In a further embodiment, a method for assembling a rotor assembly is provided. The method may include the step of preparing a first rotor shaft assembly comprising a first rotor, a second rotor, and a first shaft, wherein the first rotor and the second rotor are coaxially aligned and fixed to the first shaft. The method further includes the step of preparing an interstage plate system comprising a first plate portion having a first recess and a second plate portion having a second recess. The method further includes the step of clamping the first plate portion and the second plate portion around a first shaft, wherein the first plate portion and the second plate portion together form an interstage plate positioned between the first rotor and the second rotor, wherein the first recess and the second recess are opposing, continuous recesses, and together form a first opening through which the interstage plate passes, and the first shaft passes through the first opening.

[0014] The method may further include the step of preparing a second rotor shaft assembly comprising a third rotor, a fourth rotor, and a second shaft. The third and fourth rotors can be fixed coaxially aligned with the second shaft. The first plate portion may further comprise a third recess. The second plate portion may further comprise a fourth recess. The clamping step may be performed such that the interstage plate is positioned between the third and fourth rotors, and the third and fourth recesses are opposing, continuous recesses that together form a second opening through the interstage plate, and the second shaft passes through the second opening.

[0015] In a further embodiment, a method for assembling a vacuum pump is provided. The method includes the step of assembling a rotor assembly according to any of the embodiments described above. The method includes the step of preparing a stator comprising a pump chamber and a plate seat formed from one or more walls of the pump chamber. The plate seat is formed between a first pump stage and a second pump stage of the vacuum pump. The method further includes the steps of inserting the rotor assembly into the pump chamber, thereby moving the interstage plate into contact with the plate seat, and fastening the interstage plate to the plate seat.

[0016] Inserting the rotor assembly into the pump chamber may involve moving the rotor assembly vertically, for example, vertically downward.

[0017] The present invention will be described below merely illustratively with reference to the accompanying drawings. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic diagram showing a perspective view of one embodiment of an interstage plate system for forming interstage plates used in a vacuum pump (not to scale). [Figure 2] This is a schematic diagram (not to scale) showing an inter-stage plate formed by combining the components of an inter-stage plate system. [Figure 3] FIG. 1 is a schematic view showing an example of a rotor shaft assembly for a vacuum pump (not to scale). [Figure 4] FIG. 2 is a process flow chart showing specific steps of a method of assembling a vacuum pump. [Figure 5] FIG. 3 is a schematic view showing a specific stage of a method of assembling a vacuum pump (not to scale). [Figure 6] FIG. 4 is a schematic view of an assembled vacuum pump (not to scale). [Figure 7] FIG. 5 is a schematic view showing a perspective view of first and second rotor shaft assemblies positioned with respect to a plate portion of an interstage plate system (not to scale). [Figure 8] FIG. 6 is a schematic view showing a perspective view of an interstage plate clamped around first and second rotor shafts (not to scale). [Figure 9] FIG. 7 is a schematic view showing a perspective view of a part of a stator of a vacuum pump (not to scale). [Figure 10] FIG. 8 is a schematic view showing a perspective view of a rotor assembly inserted into a stator (not to scale). DETAILED DESCRIPTION OF THE INVENTION

[0019] In this specification, relative terms such as upper and lower, horizontal and vertical, top and bottom, front and rear are used merely to facilitate reference to the drawings, and these terms are not so limited, and it should be understood that they can implement any two different directions or positions, etc., rather than truly upper and lower, horizontal and vertical, top and bottom, etc.

[0020] FIG. 1 is a schematic view showing a perspective view of an embodiment of an interstage plate system 100 for forming an interstage plate used in a vacuum pump (not to scale).

[0021] The interstage plate system 100 includes a first plate portion 101 and a second plate portion 102.

[0022] In this embodiment, the first plate portion 101 is generally a plate material in a half-stadium shape. The first plate portion 101 includes a first mating surface 104 and a first outer surface 106 on the side opposite to the first mating surface 104. The first plate portion 101 includes two recesses formed in the first mating surface 104, and hereinafter, these two recesses are referred to as the "first recess" 108 and the "third recess" 110. The first recess 108 and the third recess 110 are substantially semi-circular. The first recess 108 and the third recess 110 are substantially the same size. The first plate portion 101 includes a first tab 112 extending from the central portion of the first outer surface 106. The first plate portion 101 includes two first fastening holes 114 penetrating the first tab 112 from the first side surface of the first plate portion 101 to the second side surface opposite to the first side surface of the first plate portion 101. The first plate portion 101 includes two second fastening holes 116 penetrating the first plate portion 101 from the first outer surface 106 to the first mating surface 104. The first plate portion 101 includes two first dowel holes 118 extending from the first mating surface 104 into the first plate portion 101. The first plate portion 101 can be formed from any suitable material such as gray cast iron, or SG iron, or Ni resist.

[0023] In this embodiment, the second plate portion 102 is a plate material that is generally half-stadium shaped. The second plate portion 102 comprises a second mating surface 120 and a second outer surface 122 opposite to the second mating surface 120. The second plate portion 102 comprises two recesses formed in the second mating surface 120, which are hereafter referred to as the "second recess" 124 and the "fourth recess" 126. The second recess 124 and the fourth recess 126 are substantially semicircular. The second recess 124 and the fourth recess 126 are substantially the same size. The second recess 124 and the fourth recess 126 are substantially the same size as the first recess 108 and the third recess 110. The second plate portion 102 includes a second tab 128 and a third tab 130, respectively, extending from the second outer surface 106 opposite to the second recess 124 and the fourth recess 126. The second plate portion 102 includes two third fastening holes 132 that penetrate the second tab 128 and the third tab 130, respectively, from the first side of the second plate portion 102 to the second side of the second plate portion 102 opposite to the first side. The second plate portion 102 includes two fourth fastening holes 134 extending into the second plate portion 102 from the second mating surface 120. The second plate portion 102 includes two second dowel holes 136 extending into the second plate portion 102 from the second mating surface 120. The second plate portion 102 further includes a fifth recess 138 formed on the second outer surface 122. More specifically, in this embodiment, the fifth recess 138 is formed in the central portion of the second outer surface 122 between the second tab 128 and the third tab 130. The second plate portion 102 can be formed from any suitable material such as gray cast iron, SG iron, or Ni-Resist.

[0024] The inter-stage plate system 100 further comprises two dowels 140 and two fasteners 142.

[0025] Dowel 140 can be formed from any suitable material, such as high-carbon steel.

[0026] The components of the interstage plate system 100 are configured to be joined together to form an interstage plate for a vacuum pump.

[0027] Figure 2 is a schematic diagram (not to scale) showing the inter-stage plate 200 formed by combining the components of the inter-stage plate system 100.

[0028] In this embodiment, the first plate portion 101 and the second plate portion 102 are joined such that the first mating surface 104 abuts against the second mating surface 120. In this configuration, each dowel 140 is positioned within the respective pairs of first and second dowel holes 118, 136. The dowels 140 help to ensure accurate alignment between the first plate portion 101 and the second plate portion 102. The first plate portion 101 and the second plate portion 102 are fixedly attached to each other by fasteners 142. Each fastener 142 is secured through its respective pair of holes, specifically the second fastening hole 116 and the fourth fastening hole 134.

[0029] In this embodiment, the first plate portion 101 and the second plate portion 102 are joined to each other such that the first recess 108 is aligned with or opposite to the second recess 124. Thus, in this configuration, the first recess 108 and the second recess 124 are opposing, continuous recesses, and together these recesses form a first opening 201 that penetrates the interstage plate 200 from a first side of the interstage plate 200 to a second side of the interstage plate 200 opposite to the first side. In this embodiment, the first opening 201 is substantially circular, i.e., a substantially cylindrical passage that penetrates the interstage plate 200.

[0030] In this embodiment, the first plate portion 101 and the second plate portion 102 are joined to each other such that the third recess 110 is aligned with or opposite to the fourth recess 126. Thus, in this configuration, the third recess 110 and the fourth recess 126 are opposing, continuous recesses, and together these recesses form a second opening 202 that penetrates the interstage plate 200 from the first side of the interstage plate 200 to the second side of the interstage plate 200. In this embodiment, the second opening 202 is substantially circular, i.e., a substantially cylindrical passage that penetrates the interstage plate 200.

[0031] Figure 3 is a schematic diagram (not to scale) showing an example of a rotor shaft assembly 300 for a vacuum pump, and will be referred to hereafter as the first rotor shaft assembly 300. The rotor shaft assembly 300 can be a composite rotor or a compound rotor.

[0032] In this embodiment, the first rotor shaft assembly 300 comprises a first rotor 301, a second rotor 302, and a first shaft 304. The first rotor 301 and the second rotor 302 are fixed to the first shaft 304 in a coaxial alignment. Thus, the first rotor 301 and the second rotor 302 are coaxially coupled or connected via the first shaft 304.

[0033] In this embodiment, the first rotor 301 is a Roots rotor. In this embodiment, the second rotor 302 is a screw rotor, and more specifically, a clockwise screw rotor.

[0034] Figure 4 is a process flowchart showing specific steps in Method 400 for assembling a vacuum pump.

[0035] Figure 5 is a schematic diagram (not to scale) showing specific steps in Method 400 for assembling a vacuum pump.

[0036] Figure 6 is a schematic diagram of the assembled vacuum pump 600 (not to scale).

[0037] Note that some of the process steps shown in the flowchart of Figure 4 and described below may be omitted, or such process steps may be performed in a different order than those shown in Figure 4. Furthermore, although all process steps are shown as separate, chronologically consecutive steps for convenience and ease of understanding, some process steps can actually be performed simultaneously or at least overlap to some extent in time.

[0038] In step s402, the first rotor shaft assembly 300 is prepared.

[0039] In step s404, the second rotor shaft assembly is prepared. The second rotor shaft assembly is shown in Figure 5 and is indicated by reference numeral 500.

[0040] In this embodiment, the second rotor shaft assembly 500 comprises a third rotor 501, a fourth rotor 502, and a second shaft 504. The third rotor 501 and the fourth rotor 502 are fixed to the second shaft 504 in a coaxial alignment. Thus, the third rotor 501 and the fourth rotor 502 are coaxially coupled or connected via the second shaft 504.

[0041] In this embodiment, the third rotor 501 is a Roots rotor. In this embodiment, the fourth rotor 502 is a screw rotor, specifically a counterclockwise screw rotor.

[0042] In step s406, the first rotor shaft assembly 300 and the second rotor shaft assembly 500 are positioned such that the first rotor 301 and the third rotor 501 mesh with each other, and the second rotor 302 and the fourth rotor 502 mesh with each other.

[0043] In step s408, the first plate portion 101 and the second plate portion 102 are clamped around the first and second rotor shafts 304, 504. More specifically, the first plate portion 101 and the second plate portion 102 are clamped around the first and second rotor shafts 304, 504 at a position along the first and second rotor shafts 304, 504 between the meshed first and third rotors 301, 501 and the meshed second and fourth rotors 302, 502. The first plate portion 101 and the second plate portion 102 are fastened together to form the interstage plate 200 as detailed above with reference to Figure 2. Thus, the interstage plate 200 is positioned between the meshing Roots rotors 301, 501 and the meshing screw rotors 302, 502. Furthermore, the first shaft 304 passes through the first opening 201, and the second shaft 504 passes through the first opening 202.

[0044] Therefore, the interstage plate 200 connects the first rotor shaft assembly 300 and the second rotor shaft assembly 500 together, thereby forming the rotor assembly 510 for the vacuum pump 600.

[0045] Figure 7 is a perspective view (not to scale) showing the first and second rotor shaft assemblies 300 and 500 positioned relative to the second plate portion 102 before the first plate portion 101 is attached to the second plate portion 102. The first rotor shaft 304 is positioned within the second recess 124, and the second rotor shaft 504 is positioned within the fourth recess 126.

[0046] Figure 8 is a schematic perspective view (not to scale) of the interstage plates 200 clamped around the first and second rotor shafts 304, 504 between the Roots rotors 301, 501 and the screw rotors 302, 502.

[0047] In step s410, the vacuum pump stator 512 is prepared.

[0048] The stator 512 comprises a first end wall 514 at a first end of the stator 512, a second end wall 516 at a second end of the stator 512 opposite the first end, and one or more side walls 518 positioned between the first end wall 514 and the second end wall 516. The first end wall 514, the second end wall 516, and the one or more side walls 518 define a pump chamber 520 between them. The first end wall 514 has a first opening 522 through it, which allows access to the pump chamber 520. The second end wall 516 has a second opening 524, which allows access to the pump chamber 520.

[0049] The stator 512 further comprises a seat, i.e., a plate seat 526, for receiving the interstage plate 200. In this embodiment, the plate seat 526 is a shelf-like or stepped portion projecting into the pump chamber 520 from the inner surface of one or more side walls 518. In some embodiments, the plate seat 526 may be a rim, lip, or flange extending into the pump chamber 520 from one or more walls of the stator 512.

[0050] Figure 9 is a schematic diagram showing a perspective view of a portion of the stator 512 (not to scale). Figure 9 shows the stator 512 from the first end, looking into the pump chamber 520. In this embodiment, the plate seat 526 includes a recess or offset 900. Multiple fastening holes 902 are formed in the plate seat 526.

[0051] In step s412, the rotor assembly 510 is inserted into the stator 512. More specifically, the rotor assembly 510 slides into the pump chamber 520 of the stator 512, with the second and fourth rotors 302, 502 first passing through the first opening 522, until the interstage plate 200 engages with the plate seat 526. The interstage plate 200 can engage with the plate seat 526 in a substantially sealed manner. The direction of movement of the rotor assembly 510 relative to the stator 512 is indicated in Figure 5 by dashed arrows and reference numeral 528.

[0052] In this embodiment, when the rotor assembly 510 is inserted into the stator 512, the first and second shafts 304, 504 extend beyond the ends of the stator 512 through the first and second openings 522, 524.

[0053] In this embodiment, the plate seat 526 defines an opening within the pump chamber 520 that is large enough to allow the passage of the second and fourth rotors 302, 502, but small enough to prevent the passage of the interstage plate 200.

[0054] Preferably, the stator 512 and rotor assembly 510 are oriented such that the movement of the rotor assembly 510 into the stator 512 is vertically downward, and can be further assisted by gravity. Therefore, when the rotor assembly is released from any insertion device, the interstage plate 200 remains engaged with the plate seat 526 due to the action of gravity.

[0055] In this embodiment, when the interstage plate 200 engages with the plate seat 526, the fifth recess 138 aligns with the recess 900 of the plate seat. The fifth recess 138 and the recess 900 of the plate seat form a flow path for the fluid pumped from the first side of the interstage plate 200 (i.e., the first pump stage including the first and third rotors 301, 501) to the second side of the interstage plate 200 (i.e., the second pump stage including the second and fourth rotors 302, 502). In other words, the fifth recess 138 and the recess 900 of the plate seat form the discharge port of the first pump stage and the inlet to the second pump stage. The interstage plate 200 defines and isolates the first and second pump stages.

[0056] Figure 10 is a schematic perspective view (not to scale) of the rotor assembly 510 inserted into the stator 512, and the first rotor shaft assembly 300 is omitted for ease and clarity of depiction.

[0057] In step s414, the inter-stage plate 200 is fixedly attached to the plate seat 526. In this embodiment, the inter-stage plate 200 is fixed to the plate seat 526 using a plurality of fasteners. Each fastener passes through the first fastening hole 114 and the third fastening hole 132, respectively, and is positioned within the respective fastening holes 902 of the plate seat 526.

[0058] In step s416, the first and second head plates of the support members 601 and 602 are positioned to support the first and second shafts 304 and 504 at the ends of the stator 512, as schematically shown in Figure 6.

[0059] More specifically, the first support member 601 is positioned at the first end of the stator 512 to mount or support the first and second shafts 304, 504. The first support member 601 includes a bearing to which the first and second shafts 304, 504 are mounted. The first seal gasket 603 is positioned between the first support member 601 and the first wall 514 of the stator 512, forming a seal between them.

[0060] Furthermore, the second support member 602 is positioned at the second end of the stator 512 to mount or support the first and second shafts 304, 504. The second support member 602 includes a bearing to which the first and second shafts 304, 504 are mounted. The second seal gasket 604 is positioned between the second support member 602 and the second wall 516 of the stator 512, forming a seal between them.

[0061] Thus, a method 400 for assembling a vacuum pump 600 is provided. The method includes providing an axially aligned rotor assembly. An interstage plate is positioned between the Roots stage and the screw stage and fastened together (e.g., screwed). Next, the twin rotor assembly, together with the interstage plate, is slid into the screw stator, preferably vertically. Next, the interstage plate is secured to the stator using a number of fasteners. Next, the Roots stage rotor is seated without gaps on the interstage plate. This positioning surface becomes the rotor mounting surface as the pump assembly progresses.

[0062] In some embodiments, the interstage plate 200 can be formed from the same material as the stator 512.

[0063] During operation, the rotor shafts 304, 504, and therefore the rotors 301, 501, 302, 302, are rotated by a motor. The rotation of the Roots rotors (i.e., the first and third rotors 301, 501) by the motor causes process gas to be drawn through a gas inlet formed in the stator 512 into the first pump stage of the pump chamber 520, in which the Roots rotors 301, 501 are rotating. Due to the continuous rotation of the rotors 301, 501, 302, 302, the process gas travels through the first pump stage of the pump chamber 520 from the gas inlet of the vacuum pump 600 to the discharge port of the first pump stage, which is formed by the fifth recess 138 and the recess 900 of the plate seat. The process gas is then pushed out of the discharge port and flows into the second pump stage of the pump chamber 520, in which the screw rotors 301, 501 (i.e., the second and fourth rotors 302, 502) are rotating. Due to the continuous rotation of the screw rotors 302 and 502 by the motor, the process gas moves from the inlet of the second pump stage (formed by the fifth recess 138 and the recess 900 of the plate seat) through the second pump stage of the pump chamber 520 to the outside of the vacuum pump 100 via the gas outlet formed in the stator 512.

[0064] Advantageously, the above-described system and method help facilitate the precise positioning and fixing of the interstage plates. It helps provide a secure position for the interstage plates.

[0065] Advantageously, it helps to facilitate the design of integrated rotors and integrated stators. For example, the first end walls of the stator may have openings through which, for example, a person or tool (such as a machining tool) can access the pump chamber during the fabrication, maintenance, or repair of the stator. An integrated stator helps to provide improved heat transfer between the inlet and exhaust ends of the pump stator.

[0066] Advantageously, the above-described system and method help to enable the fixing of interstage plates within the stator without using any radial fasteners that penetrate the stator wall.

[0067] In the above embodiment, the tip diameter of the Roots rotor is larger than the outer diameter of the screw rotor. This helps to enable the formation of an axial positioning surface (i.e., a plate seat) for the interstage plate.

[0068] Joining the first and second plate sections together with dowels helps to enable precise alignment of this section.

[0069] The inter-stage plate portion can be equipped with a machined surface suitable for plating.

[0070] In the embodiments described above, the first and second plate portions are generally half-stadium shaped. However, in other embodiments, one or both of the first and second plate portions have different shapes.

[0071] In the above embodiment, each of the first and second plate portions has two recesses formed on its mating surface. However, in other embodiments, one or both of the first and second plate portions have a different number of recesses formed on their mating surfaces.

[0072] In the above embodiment, the recesses formed on the mating surfaces of the first and second plate portions are substantially semicircular and substantially the same size as each other. However, in other embodiments, one or more of these recesses may have different suitable shapes and / or sizes.

[0073] In the embodiments described above, each of the first and second plate portions has one or more tabs formed through which the first fastening holes pass. However, in other embodiments, one or both of the first and second plate portions have a different number and / or configuration of tabs and / or first fastening holes than described above. In some embodiments, the tabs can be omitted, and one or more first fastening holes can be formed through the body of the plate portion.

[0074] In the above embodiment, each of the first plate portion and the second plate portion has two dowel holes. However, in other embodiments, each of the first plate portion and the second plate portion has a different number of dowel holes, for example, three or more dowel holes. The inter-stage plate system may have a different number of dowels, for example, three or more dowels.

[0075] In the above embodiment, each of the first and second plate portions is provided with two second fastening holes, thereby securely fastening the plate portions together. However, in other embodiments, each of the first and second plate portions is provided with a different number of second fastening holes, for example, three or four or more second fastening holes. The interstage plate system may be provided with a different number of fasteners for fastening the first and second plate portions together.

[0076] In the above embodiment, the second plate portion includes a fifth recess formed in the central part of the second outer surface between the second tab and the third tab. However, in other embodiments, the fifth recess is formed at a different location on either the second or first plate portion. The plate seat portion may include a correspondingly positioned recess that aligns with the fifth recess.

[0077] In the above embodiment, the first and third rotors are Roots rotors. However, in other embodiments, the first and third rotors are different types of rotors.

[0078] In the embodiments described above, the second and fourth rotors are screw rotors. However, in other embodiments, the second and fourth rotors are different types of rotors.

[0079] In the above embodiment, the vacuum pump comprises two rotor shaft assemblies. However, in other embodiments, the vacuum pump comprises a different number of rotor shaft assemblies.

[0080] In the above embodiment, the vacuum pump comprises two pump stages. However, in other embodiments, the vacuum pump comprises a different number of pump stages. Each interstage plate of the type described herein can be positioned between each pair of consecutive pump stages.

[0081] While exemplary embodiments of the present invention are disclosed in detail herein with reference to the accompanying drawings, it should be understood that the present invention is not limited to the exact embodiments, and various modifications and changes can be made by those skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents. [Explanation of Symbols]

[0082] 100-segment plate system 101 First plate section 102 Second plate section 104 First mating surface 106 First outer surface 108 First recess 110 Third recess 112 First tab 114 First fastening hole 116 Second fastening hole 118 First dowel hole 120 Second mating surface 122 Second outer surface 124 Second recess 126 The fourth recess 128 Second tab 130 Third tab 132 Third fastening hole 134 Fourth fastening hole 136 Second dowel hole 138 The fifth recess 140 Doubt 142 Fasteners 200-step spacing plate 201 First opening 202 Second opening 300 First rotor shaft assembly 301 First Rotor 302 Second rotor 304 First shaft 400 ways S402-S416 Method Steps 500 Second rotor shaft assembly 501 Third Rotor 502 Fourth Rotor 504 Second shaft 512 stata 514 First End Wall 516 Second End Wall 518 One or more side walls 520 Pump Room 522 First opening 524 Second opening 526 Plate seat 528 directions 600 Vacuum Pump 601 First headplate 602 Second head plate 603 First seal gasket 604 Second seal gasket 900 offset 902 Fastening hole

Claims

1. The first mating surface includes a first plate portion with a first recess, The second mating surface includes a second plate portion with a second recess, A stepped plate system comprising, The first plate portion further comprises a third recess on the first mating surface, The second plate portion further comprises a fourth recess on the second mating surface, The first plate portion and the second plate portion are joined together to form an interstage plate for a vacuum pump, and further The first mating surface and the second mating surface come into contact with each other. The first recess and the second recess are opposing, continuous recesses, and together they form an opening that penetrates the interstage plate. The third recess and the fourth recess are opposing, continuous recesses, and together they form a further opening that penetrates the interstage plate. It is configured in such a way, An inter-stage plate system in which the first plate portion and the second plate portion are fixedly attached together by fasteners passing through pairs of fastening holes that extend through the first and second mating surfaces.

2. The first plate portion is provided with two first dowel holes extending from the first mating surface into the first plate portion, The second plate portion is provided with two second dowel holes extending from the second mating surface into the second plate portion, The inter-stage plate system according to claim 1, further comprising two dowels positioned within each pair of the first dowel holes and the second dowel holes.

3. The interstage plate system according to any one of claims 1 to 2, wherein the first plate portion comprises a first outer surface opposite to the first mating surface and a first tab extending from the first outer surface, the first tab including a first tab fastening hole passing through the first tab from a first side surface of the first plate portion to a second side surface of the first plate portion.

4. The interstage plate system according to any one of claims 1 to 3, wherein the second plate portion comprises a second outer surface opposite to the second mating surface, and a second tab and a third tab extending from the second outer surface, each of the second tab and the third tab including a second tab fastening hole that passes through one of the second tab and the third tab from a first side surface of the second plate portion to a second side surface of the second plate portion.

5. The inter-stage plate system according to claim 4, wherein the second plate portion comprises a fifth recess formed in the central portion of the second outer surface between the second tab and the third tab.

6. The interstage plate system according to any one of claims 1 to 4, wherein the second plate portion comprises a fifth recess formed on a surface of the second plate portion other than the second mating surface.

7. A rotor assembly for a vacuum pump, wherein the rotor assembly is An interstage plate formed by the interstage plate system according to any one of claims 1 to 6, The first rotor and The second rotor, The first shaft and Equipped with, The first rotor and the second rotor are fixed to the first shaft, aligned coaxially. The first shaft passes through the opening in the interstage plate formed by the first recess and the second recess, The interstage plate is positioned between the first rotor and the second rotor. The rotor assembly further The third rotor, The fourth rotor, The second shaft, Equipped with, The third rotor and the fourth rotor are fixed to the second shaft, aligned coaxially. The second shaft passes through further openings in the interstage plate formed by the third recess and the fourth recess. The interstage plate is positioned between the third rotor and the fourth rotor. A rotor assembly in which the second shaft is substantially parallel to the first shaft.

8. The rotor assembly according to claim 7, wherein the first rotor and the third rotor are Roots rotors, and the second rotor and the fourth rotor are screw rotors.

9. The rotor assembly according to claim 7 or 8, wherein the first rotor and the third rotor mesh together, and the second rotor and the fourth rotor mesh together.

10. A stator having a pump chamber, A rotor assembly according to any one of claims 7 to 9, at least partially disposed within the pump chamber, A vacuum pump equipped with the following features.

11. The stator comprises a plate seat formed from one or more walls of the pump chamber, the plate seat formed between the first pump stage and the second pump stage of the vacuum pump, The vacuum pump according to claim 10, wherein the interstage plate is fixedly attached by engaging with the plate seat portion.

12. The vacuum pump according to claim 10 or 11, wherein the interstage plate is formed from the same material as the material on which the stator is formed.

13. A method for assembling a rotor assembly, wherein the method is The first rotor and The second rotor, The first shaft and, The steps include: preparing a first rotor shaft assembly comprising the first rotor and the second rotor being fixed to the first shaft in a coaxial arrangement; The third rotor, The fourth rotor, The second shaft, The steps include: preparing a second rotor shaft assembly comprising the third rotor and the fourth rotor being fixed to the second shaft in a coaxial arrangement; The first mating surface includes a first plate portion with a first recess and a third recess, The second mating surface includes a second plate portion with a second recess and a fourth recess, The steps include: preparing an inter-stage plate system equipped with; The first plate portion and the second plate portion together form an interstage plate that is positioned between the first rotor and the second rotor, and between the third rotor and the fourth rotor. The first recess and the second recess are opposing, continuous recesses, and together they form a first opening that passes through the interstage plate. The third recess and the fourth recess are opposing, continuous recesses, and together they form a second opening that passes through the interstage plate. The first shaft passes through the first opening, The second shaft passes through the second opening. The steps include clamping the first plate portion and the second plate portion around the first shaft and the second shaft; Includes, The clamping step is, The steps include bringing the first mating surface and the second mating surface into contact, The steps include fastening the first plate portion and the second plate portion using fasteners that pass through pairs of fastening holes extending through the first mating surface and the second mating surface, Methods that include...

14. A method for assembling a vacuum pump, The steps of assembling a rotor assembly by the method of claim 13; The pump room and A plate seat portion formed from one or more walls of the pump chamber, and formed between the first pump stage and the second pump stage of the vacuum pump, The steps include: preparing a stator equipped with; The steps include: inserting the rotor assembly into the pump chamber, thereby moving the interstage plate to contact the plate seat; The steps include fastening the interstage plate to the plate seat; Methods that include...

15. The method according to claim 14, wherein inserting the rotor assembly into the pump chamber includes moving the rotor assembly in a vertical direction.

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