TW200817592A - Vacuum pump - Google Patents

Abstract

A dry vacuum pump comprises a stator component and at least one rotor component. To improve the tolerance of the pump to corrosive gases and abrasive particles passing through the pump, the stator component and/or said at least one rotor component are formed from austempered ductile iron.

Description

200817592 IX. Description of the invention: [Technical field to which the invention pertains] The present invention relates to a dry vacuum pump. [Prior Art] Dry vacuum pumps are widely used in industrial processes to provide a clean and/or low pressure environment for manufacturing products. Applications include the pharmaceutical, semiconductor and flat panel industries. These pumps include a substantially dry (or oil-free) pump mechanism, but the system also includes certain components for driving the pump mechanism (which require lubricating oil to be effective), such as bearings and transfer gears. Examples of dry pumps include Roors pumps, Northey (or "claw" pumps, screw pumps, and scroll pumps. Dry pumps with Roots and/or Norther rotor assemblies are typically multi-stage A positive displacement pump comprising a stator assembly defining a plurality of pump chambers each accommodating a pair of mutually intermeshing rotor assemblies. The rotor assembly is located on the countershaft and is in each chamber Having the same type of profile or profile can vary from chamber to chamber. Iron castings have long been used to make stator and rotor assemblies for dry vacuum pumps. However, in the semiconductor industry, relatively high corrosive rolling stocks with high flow rates (such as The ever-increasing use of gas, boron trichloride, hydrogen bromide, fluorine gas and trifluorocarbon gas has led to severe corrosion and thus to a relatively short service life of cast iron stator and rotor assemblies. In addition to the cost associated with the replacement of corroded parts and consequent process downtime, this corrosion can result in equipment failure, process gas leaks, and possible process contamination. It is known to form a resin containing 120364.d〇i 200817592 rat polymer or polyimine material on the surface of the component to the corrosive gas. These components are known to be passively oriented. i 泠 9 9 has a tilting gas that degrades over time. g H under cast iron is exposed to corrosive and right 徉 sound center “(for example, ductile corrosion resistant Ni cast iron) or eight helmets with good corrosion resistance. Temple, and pieces. However, the Nico-resistant iron and stainless steel are relatively expensive and the furnace; a M process' and therefore for the use in the manufacture of rotors and tweezers components. 叩 is not as cost effective SUMMARY OF THE INVENTION The present invention provides a dry vacuum pump _ ^ /, 匕 3 a raft subassembly and at least one rotor assembly, wherein the stator group sighs / or the at least one Korean Newlin is ductile by Auschine tempering The stator assembly can accommodate first and second mutually reciprocating rotor assemblies that are adapted to be reversed within the stator assembly. In a preferred embodiment, the rotor assembly has a Roots profile, although it can be right eight if desired J has Noser or screw wheel The pump may be in the form of a multi-stage pump, wherein the stator assembly defines a pump chamber that is arranged in series and each accommodates a plurality of interconnected interconnects of the respective rotor assemblies formed by the tempering of the austenite. The intermeshing rotor assemblies can be located on the respective shafts - the middle pockets 3 are used to transmit the torque from one shaft to the other of the gear assemblies 'where the gear assembly is at least _ the gears are preferably ductile irons that are tempered by Auschine Alternatively, the fruit may be in the form of a spiral wrap, wherein the ^zaki comprises a fixed scroll member having an end plate having a first spiral cladding extending therefrom and the at least one rotor assembly A rotary 120364.doc 200817592 scroll member having an _ end plate is provided, the end plate having a second spiral cover extending therefrom to repel each other with the first spiral cover. Each of the scroll members is preferably formed by interest. The ADI preferably has a graphite spheroidization rate of at least 9%. ADI preferably has a matrix of acicular ferrite and carbon stabilized austenite. The ductile iron which has been austempered by austenite preferably comprises one or more of the following elements: carbon in the range of 3.4 to 3.5% by mass; in the range of 2 to 2.3% by mass; Manganese in total in the range of 〇·〇75 to 〇·15% by mass, total by mass in the range of 3.4 to 3.5% by mass; total by mass in the range of 1-2 to 1.4% Nickel inside; and copper in total in the range of 〇.75 to 〇· 9.5 % by mass. [Embodiment] Referring to Figures 1 and 2, a multi-stage dry vacuum pump 1A includes a stator assembly 12 preferably formed of an austempered ductile iron (ADI) having a plurality of pump chambers A series of walls of chambers 14, 16, 18, 20, 22. An inlet conduit 24 for delivering gas to pump the inlet pump chamber 14 and a discharge conduit 26 for discharging the pumped gas from the discharge chest chamber 22 are also formed in the stator 12. The circumferential passages 28, 3, 32 and 34 formed in the stator 12 are connected in series to the pump chambers 14, 16, 18, 20, 22. The stator 12 houses a first shaft 36 and a second shaft 38 spaced from the first shaft 36 and parallel to the first shaft 36. Bearings 4 for supporting the shafts 36, 38 are provided in the end plates 42, 44 of the stator 12. One of the shafts 36 is coupled to a drive motor 46 that is coupled together by a timing gear 47 such that in use the shafts 36, 38 rotate at the same speed but in opposite directions, as indicated by arrow 48 in FIG. Arrow 120364.doc 200817592 50 indicates. The gearbox 52 attached to the side of the pump ι contains oil 54 for lubricating the timing gear 47. The timing gear 47 can be formed by ADI. Within each pump chamber, the shafts 36, 38 support respective rotor assemblies 56, 58 that may also be formed by ADI. While a mixture of Roots and Nose profiles can be provided within pump 10, in this embodiment, rotors 56, 58 have a Roots-type profile within each pump chamber. The rotors 56, 58 are located in each of the pump chambers relative to the inner surface of the stator 12 such that the rotors 56, 58 can operate in a manner known per se. In use, gas is pushed into the pump 1 through the inlet conduit 24 and into the inlet pump chamber 14 . The gas is compressed by the rotors 56, 58 located within the inlet fruit chamber 14 and fed by the passage 28 into the next pump chamber 16. The gas fed into the pump chamber 16 is similarly compressed by the rotors %, 58 located therein and fed by the passage 30 to the next pump chamber 18. Similar gas compression occurs in the pump chambers 18, 20 and 22, wherein the pumped gas is ultimately discharged from the pump 10 via the discharge conduit 26. The use of austenitic tempered ductile iron (ADI) to manufacture the pump assembly 1 and/or rotor assemblies 56, 58 makes the pump 1 〇 particularly suitable for pumping corrosive gases such as chlorine 'boron trichloride, bromine Hydrogen, fluorine gas and chlorine trifluoride. ADI has superior hardness, higher specific strength ratio, and comparable 匕 corrosion sensitivity compared to the more expensive corrosion resistant materials currently available four to five times more expensive than ADI. This allows the stator and rotor assembly and timing gear to have relatively high grind and corrosion resistance with reduced component weight and cost for equal or improved performance. As an example, the ductile iron (fine) of the austempered temper used to make the stator assembly 12 and/or the rotor assembly 56, 120364.doc 200817592 58 and/or the timing gear 47 may include the following elements (by mass): Element---*-----% carbon 3·4 to 3.5 矽2.0 to 2.3 violent 0.2 to 0.22 molybdenum "0.075 to 0.15 nickel 1.2 to 1.4 copper 0.75 to 0.95 preferably having a graphite spheroidization rate of at least 90% and Preferably, the number of spheroidal particles in the range of 15 Å to 300/mm is preferred. ADI preferably has a major matrix of acicular ferrite and carbon-stabilized austenite, which is substantially free of carbides, inclusions or porosity. These features enable the material to meet semiconductor processing

The performance requirements of U are notable for sufficient friction and mechanical properties at high temperatures and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross section through a multistage dry vacuum pump; and Fig. 2 is a view along line a-Α in Fig. 1. [Main component symbol description] 10 Pump 12 Stator/stator assembly 14 Pump chamber 16 Pump chamber 18 Pump chamber 20 Pump chamber 120364.doc 200817592 22 24 26 28 30 32 34 36 38 40 42 44 46 47 48 50 52 54 56 58 Pump chamber inlet pipe discharge pipe circumferential channel circumferential channel circumferential channel circumferential channel suction bearing end plate end plate drive motor timing gear arrow arrow gearbox oil rotor / rotor assembly rotor / rotor assembly 120364.doc -10-

Claims (1)

200817592 Patent Application Range: 1. A dry vacuum fruit comprising a stator assembly and at least a rotor implant wherein the stator assembly and/or the at least rotor set (4) is formed from an austempered ductile iron. 2. As claimed in the at least one of the rotor assemblies having a screw profile, a Roots profile or a Noosaer gallery. 3. The pump of claim 2, which comprises a first and second intermeshing rotor assembly adapted to reverse within the stator assembly. Γ 4. The pump of claim 3, in the form of a multi-stage dry vacuum fruit, wherein the sub-components are defined (four) and each accommodates - a plurality of interconnected fruit chambers for the respective rotor assemblies Each rotor assembly is formed from ductile iron that has been tempered by Auer. 5. The system of claim 3, wherein the rotor assembly is located on each of the shafts, the system includes - a gear assembly for transmitting torque from the shaft to the gear assembly of the other shaft - at least one gear of the gear assembly Formed by ductile iron that is tempered by austenite. 6. The request item! The chestnut is in the form of a scroll spring, wherein the stator assembly comprises a fixed scroll member having an end plate having a first spiral coating extending therefrom And the at least-rotor assembly comprises a rotary wrap member having an end plate having a second spiral cladding extending therefrom for engaging the first spiral cover. 7. The system of any of the preceding claims, wherein the austenitic tempered ductile iron has a graphite spheroidization rate of at least 90%. 8. The pump of any of the claims (1), wherein the ductility of the Auger tempering is 120364.doc 200817592 9. 10. The iron has a matrix of acicular ferrite and carbon stabilized austenite. The pump according to any one of items 1 to 6, wherein the austenitic tempered ductile iron comprises carbon in a total amount of 3.4 to 3.5% by mass. A pump according to any one of claims 1 to 6, wherein the austenitic tempered ductile iron comprises a total of 2 to 2 3% by mass. The pump according to any one of the preceding claims, wherein the ductile iron which has been austempered by austery comprises manganese in a total amount of from 〇.075 to 〇15% by mass. The pump of any one of claims 1 to 6, wherein the austenitic tempered ductile iron comprises a total of 3.4 to 3.5% by mass. The pump of any one of claims 1 to 6, wherein the austenitic tempered ductile iron comprises nickel in total in the range of 1.2 to 1.4% by mass. The pump of any one of claims 1 to 6, wherein the austenitic tempered ductile iron comprises copper in a total amount ranging from 0.75 to 0.95% by mass. 120364.doc