Stator for vacuum pump

Abstract

At least a portion of a stator (118) for a vacuum pump (100) comprises: a plurality of walls (152, 154) defining at least a portion of a pump chamber (171) therebetween; a flow passage (182) formed in one or more walls (152) of the plurality of walls (12, 154), the flow passage (182) having a first opening (184) at a first end of the flow passage (182) and a second opening (186) at a second end of the flow passage (182), the first opening (184) being an opening in an inner surface of the one or more walls (152) and in fluid communication with the pump chamber (171); and a pressure relief valve (190) disposed in the flow passage (182).

Description

Technical Field

[0001] The present invention relates to a stator for a vacuum pump and its components.

Background Art

[0002] Vacuum pumps are used to pump gas from a process chamber in various technical processes, thereby creating low-pressure conditions for each process.

Summary of the Invention

Means for Solving the Problems

[0003] The inventors recognize that during use, the pressure difference within the pump chamber of a vacuum pump can reach or exceed a level that can damage the components of the vacuum pump. For example, the pressure difference across the rotor between the suction side and the exhaust side of the pump chamber can be high enough to damage the pump's rotor, shaft, and / or bearings. Therefore, a pressure relief system including a pressure relief valve for the pump chamber is desirable. The inventors recognize that placing a pressure relief valve in a relatively cold part of the pump, such as the head plate, risks contamination or damage to the pressure relief valve by condensate from the pumped fluid. The inventors recognize that by placing the pressure relief valve in a relatively hot part of the pump, such as the wall of the stator, the amount of condensate can be reduced.

[0004] In one aspect, at least a part of a stator for a vacuum pump is provided, and at least a part of the stator has an integrated or integral pressure relief system including a pressure relief valve.

[0005] In one aspect, at least a part of a stator for a vacuum pump is provided, and at least a part of the stator includes: a plurality of walls that define at least a part of a pump chamber therebetween; a flow path formed in one or more of the plurality of walls, the flow path including a first opening at a first end of the flow path and a second opening at a second end of the flow path, the first opening being an opening on an inner surface of one or more of the walls and being in fluid communication with the pump chamber, the flow path; and a pressure relief valve disposed in the flow path.

[0006] The first opening can be disposed on the exhaust side of the pump chamber.

[0007] The second opening can be an opening on an inner surface of one or more of the walls and is in fluid communication with the pump chamber. The second opening can be disposed on the suction side of the pump chamber.

[0008] The pressure relief valve can be disposed in a housing that is removable from at least a part of the stator through an opening on an outer surface of at least a part of the stator.

[0009] The plurality of walls can include an end wall and one or more side walls extending from the end wall. The end wall and the one or more side walls can define an internal cavity. The flow path can be formed in the end wall. The first opening can be formed on the inner surface of the end wall. The second opening can be formed on the inner surface of the end wall. The end wall and the one or more side walls can be a single element. The end wall can include one or more through bores, each of the one or more through bores being for receiving a respective rotor shaft. At least a part of the stator for a vacuum pump can further include an inlet flow path formed through a side wall of the one or more side walls that enables the inflow of fluid from outside at least a part of the stator into the internal cavity. The end wall can have an outer surface, and the outer surface of the end wall includes one or more recesses. The one or more recesses can be selected from a group of recesses including a loop-shaped groove for receiving an O-ring and a recess configured to receive a heat insulating spacer. At least a part of the stator can further include an O-ring and / or one or more heat insulating spacers disposed in the one or more recesses; and a head plate for supporting the one or more rotor shafts, the head plate being disposed opposite to the outer surface of the end wall and in contact with the O-ring and / or the one or more heat insulating spacers and spaced apart from the outer surface of the end wall.

[0010] In a further aspect, a stator including at least a part of the stator according to any of the above aspects; and one or more rotor shafts extending through the pump chamber of the stator; A vacuum pump is provided that includes one or more rotors, each attached to a respective one of the rotor shafts.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0012] 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. It should be understood that they do not necessarily represent truly upper and lower, horizontal and vertical, top and bottom, etc., but can represent any two different directions or positions, etc.

[0013] FIG. 1 is a schematic side cross-sectional view of an embodiment of a vacuum pump 100 (not to scale).

[0014] FIG. 2 is a schematic front cross-sectional view of the vacuum pump 100 (not to scale).

[0015] The vacuum pump 100 is a roots-type vacuum pump with a vertical orientation.

[0016] The vacuum pump 100 includes a stator 102, a first rotor 104 attached to a first rotor shaft 106, a second rotor 108 attached to a second rotor shaft 110, a first head plate 112, and a second head plate 114.

[0017] The stator 102 includes two parts, namely a first stator part 116 and a second stator part 118. FIGS. 3 and 4 show further views of the stator 102. FIG. 3 is a schematic view showing a perspective view of the stator 102 (not to scale). FIG. 4 is a schematic view showing a perspective cross-sectional view of the stator 102 (not to scale).

[0018] The first stator part 116 and the second stator part 118 can be regarded as a bucket stator that is attached together to form the stator 102.

[0019] The first stator part 116 includes a first wall 120 and one or more first side walls 122 extending from the first wall 120. The first wall 120 can be regarded as the bottom wall or the first end wall of the stator 102. One or more first side walls 122 extend upward from the first wall 120. The first wall 120 and one or more first side walls 122 define an internal cavity. The first wall 120 and one or more first side walls 122 can be a single unitary element.

[0020] The first stator part 116 further includes an outlet flow path 124. The outlet flow path 124 is the gas outlet of the stator 102. The outlet flow path 124 is formed through one or more of the first side walls 122. The outlet flow path 124 is a flow path between a first opening 126 and a second opening 128. The first opening 126 is on the inner surface of one or more side walls 122. The second opening 128 can be present on the outer surface of one or more side walls 122, which is opposite to the inner surface of one or more side walls 122. Preferably, the outlet flow path 124 is inclined downward from the first opening 126 towards the second opening 128.

[0021] The inner surface 130 of the first wall 120 is continuous with the first opening 126 of the outlet flow path 124. Preferably, the lowermost point of the inner surface 130 of the first wall 120 is continuous with the first opening 126. Preferably, the inner surface 130 of the first wall 120 is inclined downwardly toward the first opening 126. Nevertheless, in some embodiments, the inner surface 130 can be substantially flat.

[0022] The inner surface 130 of the first wall 120 can be regarded as being in contact with, sharing a boundary with, joining, being connected to, or coinciding with the first opening 126. When viewed from the side as shown in FIG. 1, the lowermost surface 132 of the outlet flow path 124 is substantially in the same plane as the horizontal plane 134 of the inner surface 130 of the first wall 120, or more preferably, is below the horizontal plane 134. Further, when viewed from the front as shown in FIG. 2, the inner surface 130 of the first wall 120 coincides with the periphery of the first opening 126, or more preferably, is within the region surrounded by the periphery of the first opening 126.

[0023] In this embodiment, the first wall 120 includes two through bores 136. Each through bore 136 receives one of the first rotor shaft 106 and the second rotor shaft 110 respectively. In other words, the first and second rotor shafts 106, 110 pass through the first wall 120 through their respective through bores 136. The first and second rotor shafts 106, 110 can be sealed against the first wall 120 (i.e., the wall of the through bore 136) by some suitable sealing means such as a lip seal or a labyrinth seal.

[0024] In this embodiment, the outer surface 138 of the first wall 120 on the side opposite to the inner surface 130 of the first wall 120 includes a plurality of recesses. The outer surface 138 of the first wall 120 can be seen more clearly in FIG. 5, which is a schematic view (not to scale) of a perspective view of the inverted first stator portion 116.

[0025] More specifically, in this embodiment, the outer surface 138 of the first wall 120 includes a loop-shaped recess or groove 140. The loop-shaped groove 140 surrounds the through bore 136. The loop-shaped groove 140 can be disposed close to the peripheral edge of the outer surface 138.

[0026] In this embodiment, the outer surface 138 of the first wall 120 includes a plurality of recesses 142, which are substantially cylindrical in this embodiment. In this embodiment, the recesses 142 are disposed between the loop-shaped groove 140 and the edge of the outer surface 138.

[0027] Referring again to FIGS. 1 and 2, in this embodiment, a first O-ring 144 is disposed in the loop-shaped groove 140 of the outer surface 138 of the first wall 120. The first O-ring 144 can be made of some suitable material, such as polytetrafluoroethylene (PTFE). Preferably, the first O-ring 144 is made of a heat insulating material. Also, in this embodiment, a plurality of first spacers 146 are respectively disposed in the plurality of recesses 142. The first spacers 146 can be substantially cylindrical. In this embodiment, the first spacers 146 are made of a heat insulating material such as a ceramic material.

[0028] The first head plate 112 is disposed facing or opposite to the outer surface 138 of the first wall 120. The first head plate 112 is disposed in contact with the first O-ring 144 and the first spacers 146. The first O-ring 144 and / or the first spacers 146 maintain the first head plate 112 in a state separated from the outer surface 138 of the first wall 120. Accordingly, a gap 148 (e.g., an air gap) is provided between the stator 102 and the first head plate 112. The first O-ring 144 forms a seal between the stator 102 and the first head plate 112, that is, between the outer surface 138 of the first wall 120 and the opposing surface of the first head plate 112.

[0029] The first head plate 112 is configured to support the first and second rotor shafts 106, 110 at the lower ends of those rotor shafts 106, 110. The first head plate can be a conventional head plate. The first head plate 112 can include bearings and / or a seal system for supporting the rotor shafts 106, 110.

[0030] In this embodiment, one or more first side walls 122 include a first flange 150 at an end of the first side wall 122 opposite the first wall 120.

[0031] The second stator portion 118 includes a second wall 152 and one or more second side walls 154 extending from the second wall 152. The second wall 152 can be regarded as the upper wall or the second end wall of the stator 102. One or more second side walls 154 extend downward from the second wall 152. The second wall 152 and one or more second side walls 154 define an internal cavity. The second wall 152 and one or more second side walls 154 can be a single unitary element.

[0032] The second stator portion 118 further includes an inlet flow path 155. The inlet flow path 155 is the gas inlet of the stator 102. The inlet flow path 155 is formed through one or more of the second side walls 154.

[0033] In this embodiment, the second wall 152 includes two through bores 156. Each through bore 156 receives one of the first rotor shaft 106 and the second rotor shaft 110 respectively. In other words, the first and second rotor shafts 106, 110 pass through the second wall 152 through the respective through bores 156. The first and second rotor shafts 106, 110 can be sealed against the second wall 152 (i.e., the wall of the through bore 156) by some suitable sealing means such as a lip seal or a labyrinth seal.

[0034] In this embodiment, the outer surface 158 of the second wall 152 includes a plurality of recesses. The outer surface 158 of the second wall 152 can be seen more clearly in FIGS. 6 and 7, which are schematic views (not to scale) of a perspective view of the second stator portion 118.

[0035] More specifically, in this embodiment, the outer surface 158 of the second wall 152 includes a loop-shaped recess or groove 160. The loop-shaped groove 160 surrounds the through bore 156. The loop-shaped groove 160 can be disposed close to the peripheral edge of the outer surface 158.

[0036] In this embodiment, the outer surface 158 of the second wall 152 includes a plurality of recesses 162, which are substantially cylindrical in this embodiment. In this embodiment, the recesses 162 are disposed between the loop-shaped groove 160 and the edge of the outer surface 158.

[0037] Referring back to FIGS. 1 and 2, in this embodiment, a second O-ring 164 is disposed in the loop-shaped groove 160 of the outer surface 158 of the second wall 152. The second O-ring 164 can be made of some suitable material, such as polytetrafluoroethylene (PTFE). Preferably, the second O-ring 164 is made of a heat insulating material. Also, in this embodiment, a plurality of second spacers 166 are respectively disposed in the plurality of recesses 162. The second spacers 166 can be substantially cylindrical. In this embodiment, the second spacers 166 are made of a heat insulating material such as a ceramic material.

[0038] The second head plate 114 is disposed facing or opposite to the outer surface 158 of the second wall 152. The second head plate 114 is disposed in contact with the second O-ring 164 and the second spacer 166. The second O-ring 164 and / or the second spacer 166 maintain the second head plate 114 in a state separated from the outer surface 158 of the second wall 152. Accordingly, a gap 168 (e.g., an air gap) is provided between the stator 102 and the second head plate 114. The second O-ring 164 forms a seal between the stator 102 and the second head plate 114, i.e., between the outer surface 158 of the second wall 152 and the opposing surface of the second head plate 114.

[0039] The second head plate 114 is configured to support the first and second rotor shafts 106, 110 at the upper ends of those rotor shafts 106, 110. The second head plate 114 can be a conventional head plate. The second head plate 114 can include bearings and / or a seal system for supporting the rotor shafts 106, 110.

[0040] In this embodiment, one or more second side walls 154 include a second flange 170 at an end of the second side wall 154 opposite to the second wall 152.

[0041] As shown in FIGS. 1 to 4, in the assembled configuration, the second stator portion 118 is disposed on the first stator portion 116 such that the second flange 170 contacts the first flange 150. The first stator portion 116 and the second stator portion 118 are attached and fastened together by a plurality of fasteners (not shown) via the first and second flanges 150, 170.

[0042] The walls of the first stator portion 116 and the second stator portion 118, namely the first wall 120, the first side wall 122, the second wall 152 and the second side wall 154, define an internal cavity or chamber 171. This chamber 171 can also be called a stator bore. This chamber 171 is the pump chamber of the vacuum pump 100. The rotors 104, 108 are disposed within the chamber 171.

[0043] During operation, one or more motors (not shown) drive the rotor shafts 106, 110, thereby rotating the rotors 104, 108 about parallel axes within the chamber 171. This rotation of the rotors 104, 108 sucks gas into the suction side 172 of the chamber 171 through the inlet 155, as shown by the arrow and reference numeral 174 in FIG. 1. Following the continuous rotation of the rotors 104, 108, the gas moves from the suction side 172 of the chamber 171 to the exhaust side 176 of the chamber 171, as shown by the arrow and reference numeral 178 in FIG. 1. Following the continuous rotation of the rotors 104, 108, the gas moves from the exhaust side 176 of the chamber 171 to the outside of the outlet 124, as shown by the arrow and reference numeral 180 in FIG. 1.

[0044] Therefore, the rotors 104, 108 can be regarded as dividing the chamber 171 into a suction side 172 (where the inlet 155 is located) and an exhaust side 176 (where the outlet 124 is located).

[0045] The fluid (e.g., gas) pumped by the vacuum pump 100 may contain or be accompanied by particulate matter such as liquid and / or dust. Further, the pumped fluid may condense on the surface within the chamber 171. This liquid and / or particulate matter tends to fall by gravity to the bottom of the pumping chamber 171 and may accumulate on the inner surface 130 of the first wall. Advantageously, the inner surface 130 of the first wall 120 that is continuous with the first opening 126 of the outlet flow path 124 tends to cause the liquid and / or particulate matter to flow or move out of the pump chamber through the outlet 124. The outflow of this liquid and / or the removal of particulate matter from the chamber 171 tend to be further promoted by the fact that the lowermost point of the inner surface 130 is continuous with the first opening 126 and / or the inner surface 130 is inclined downward toward the first opening 126.

[0046] Accordingly, advantageously, the accumulation of potentially flammable, corrosive, or otherwise dangerous liquids and / or particulate matter within the pump chamber 171 tends to be reduced or eliminated. Further, the impedance of, for example, the rotors 104, 108 by the liquid and / or particulate matter tends to be reduced or eliminated. Accordingly, the pumping efficiency of the pump tends to be improved.

[0047] Advantageously, the spatial separation of the stator 102 from the head plates 112, 114 by the O-rings 144, 164 and the spacers 146, 166 (i.e., the presence of the gaps 148, 168 between the stator 102 and the head plates 112, 114) tends to reduce the heat transfer between the stator 102 and the head plates 112, 114. Accordingly, in embodiments where the temperature of the stator 102 is relatively high, the temperature of the head plates can nevertheless remain relatively low. For example, in some embodiments, the temperature of the stator 102 may be about 200°C, while the temperature of the head plates 112, 114 may be about 100°C. This advantageously tends to improve the operation of the vacuum pump 100.

[0048] In this embodiment, the second stator portion 118 further includes a flow path 182 formed in the second wall 152. The flow path 182 extends between a first opening 184 and a second opening 186.

[0049] In this embodiment, the first opening 184 is formed in the inner surface 188 of the second wall 152, and the inner surface 188 is on the side opposite to the outer surface 158. The first opening 184 is located on the exhaust side 176 of the chamber 171.

[0050] In this embodiment, the second opening 186 is formed in the inner surface 188 of the second wall 152. The second opening 186 is located on the suction side 172 of the chamber 171.

[0051] In this embodiment, a pressure relief valve 190 is disposed in the flow path 182 between the first opening 184 and the second opening 186. In this embodiment, the pressure relief valve 190 is configured to block the flow of fluid through the flow path 182 when the pressure difference across the pressure relief valve 190 is less than a predetermined threshold. Further, the pressure relief valve 190 is configured to allow the flow of fluid through the flow path 182 when the pressure difference across the pressure relief valve 190 is greater than or equal to a preset threshold.

[0052] Therefore, in this embodiment, during operation, when the pressure difference across the pressure relief valve 190, that is, the pressure difference between the exhaust side 176 and the suction side 172 of the chamber 171, is greater than or equal to a preset threshold, the pressure relief valve 190 opens to allow the flow of the fluid pumped through the flow path 182 from the exhaust side 176 of the chamber 171 to the suction side 172 of the chamber 171. This advantageously tends to reduce the pressure difference between the exhaust side 176 and the suction side 172. In other words, the pressure difference across the rotors 104, 108 is reduced. Therefore, the risk of damage to the rotors 104, 108 tends to be reduced.

[0053] Advantageously, fluidly connecting the flow path 182 between the exhaust side 176 and the suction side 172 tends to allow a rapid reduction in the pressure difference between the exhaust side 176 and the suction side 172. Nevertheless, in some embodiments, the flow path 182 can fluidly connect between the pump chamber 171 (e.g., the exhaust side 176 of the chamber 171) and the external environment of the pump 100.

[0054] The pressure relief valve 190 is disposed or housed within the stator 102, specifically within the second wall 152 of the stator 102 in this embodiment. The pressure relief valve 190 can be considered to be integral with the stator 102 or incorporated within the stator 102. During use, the temperature of the stator 102 tends to be relatively high compared to, for example, the temperatures of the head plates 112, 114. For example, in some embodiments, the temperature of the stator 102 is about 200 °C, while the temperatures of the head plates 112, 114 may be about 100 °C. The relatively high temperature of the stator 102 tends to reduce or eliminate condensation of the fluid pumped through the flow path 182. This advantageously tends to reduce or eliminate condensate that would otherwise impede the operation of the pressure relief valve 190.

[0055] In this embodiment, the pressure relief valve 190 is disposed within a housing removable from the stator through an opening in the side of the second end wall 152. This advantageously tends to facilitate inspection, maintenance, service, and / or repair of the pressure relief valve 190.

[0056] Advantageously, by disposing the pressure relief valve 190 at the upper part of the stator, i.e., the upper end wall, any particulate matter or fluid that enters the flow path 182 tends to fall from the flow path 182 (i.e., the duct of the pressure relief valve) rather than accumulate.

[0057] In some embodiments, the flow path 182 is a multi-branched (e.g., branched flow path) having a plurality of first openings (or inlets) and / or a plurality of second openings (or outlets). In some embodiments, a plurality of pressure relief valves can be disposed within the flow path.

[0058] In the above embodiments, the vacuum pump is a vertically oriented roots-type vacuum pump. However, in other embodiments, the vacuum pump is a different type of vacuum pump. The vacuum pump can have, for example, any number of stages, pump chambers, rotors, and rotor shafts.

[0059] In the above embodiments, the stator is formed of two parts that are attached together to form the stator. However, in other embodiments, the stator is formed of a different number of parts, such as a single part only, or three or more parts that are attached together to form the stator.

[0060] In the above embodiments, the inlet is formed in the second stator portion. However, in other embodiments, the inlet is disposed in a different stator portion, such as the first stator portion. In some embodiments, the inlet is formed through a plurality of different stator portions.

[0061] In the above embodiments, the two head plates are spaced apart from the stator. However, in other embodiments, one or more of the head plates are not spaced apart from the stator. For example, one or more of the head plates can be in contact with or integral with the stator.

[0062] In the above embodiments, the second stator portion includes a flow path in which the pressure relief valve is disposed. However, in other embodiments, the flow path and the pressure relief valve disposed therein can be disposed in a different portion of the stator, such as the first stator portion, for example, the first wall.

[0063] In the above embodiment, the outlet is formed in the first stator portion. However, in other embodiments, the outlet is disposed in a different stator portion, such as the second stator portion. In some embodiments, the outlet is formed through a plurality of different stator portions.

[0064] In the above embodiment, the inner surface of the first wall of the first stator is continuous with the opening of the outlet flow path. In other words, the lowermost surface or point of the opening is substantially in the same plane as or below the inner surface of the first wall. However, in other embodiments, the inner surface of the first wall of the first stator is not continuous with the opening of the outlet flow path. The lowermost surface or point of the opening can be located at a height exceeding the height of the inner surface of the first wall.

Description of Reference Numerals

[0065] 100 Vacuum pump 102 Stator 104 First rotor 106 First rotor shaft 108 Second rotor 110 Second rotor shaft 112 First head plate 114 Second head plate 116 First stator portion 118 Second stator portion 120 First wall 122 First side wall 124 Outlet flow path 126 First opening 128 Second opening 130 Inner surface 132 Lowermost surface 134 Horizontal plane 136 Through bore 138 Outer surface 140 Loop-shaped groove 142 Recess 144 First O-ring 146 First spacer 148 Gap 150 First flange 152 Second wall 154 Second side wall 155 Inlet path 156 Through bore 158 Outer surface 160 Loop-shaped groove 162 Recess 164 Second O-ring 166 Second spacer 168 Gap 170 Second flange 171 Chamber 172 Suction side 174 Suction gas flow direction 176 Exhaust side 178 Gas flow direction 180 Exhaust gas flow direction 182 Flow path 184 First opening 186 Second opening 188 Inner surface 190 Pressure relief valve

Claims

1. A stator for a vertically oriented vacuum pump, comprising: a plurality of walls defining at least a part of a pump chamber therebetween; a flow path formed in one or more of the plurality of walls, the flow path comprising: a first opening at a first end of the flow path and a second opening at a second end of the flow path, the first opening being an opening on an inner surface of the one or more walls, the first opening being in fluid communication with the pump chamber; a pressure relief valve disposed in the flow path; the plurality of walls including an upper end wall and one or more side walls extending downward from the upper end wall, the upper end wall and the one or more side walls defining an internal cavity; the flow path being formed in the upper end wall; the first opening being formed on an inner surface of the upper end wall, the second opening being formed on the inner surface of the upper end wall; the first opening being disposed on an exhaust side of the pump chamber; the second opening being disposed on a suction side of the pump chamber; the upper end wall having one or more through bores, each of the one or more through bores being for receiving a respective rotor shaft; the upper end wall and the one or more side walls being a single unitary element; a stator.

2. The stator according to claim 1, wherein the pressure relief valve is disposed in a housing removable from the stator through an opening on an outer surface of the stator.

3. The stator according to claim 1, further comprising an inlet flow path formed through a side wall of the one or more side walls to allow fluid to flow from outside the stator into the internal cavity.

4. The stator according to claim 1, wherein the upper end wall has an outer surface, and the outer surface of the upper end wall has one or more recesses.

5. The stator according to claim 4, wherein the one or more recesses are selected from a group of recesses including a loop-shaped groove for receiving an O-ring and a recess configured to receive a heat insulating spacer.

6. An O-ring and / or one or more heat insulating spacers disposed in the one or more recesses, A head plate for supporting one or more rotor shafts, the head plate being disposed opposite to the outer surface of the upper end wall and in contact with the O-ring and / or the one or more heat insulating spacers, and being spaced apart from the outer surface of the upper end wall, The stator according to claim 5, further comprising.

7. The stator according to claim 1, One or more rotor shafts extending vertically through the pump chamber of the stator, One or more rotors each attached to one of the respective rotor shafts, A vertically oriented vacuum pump comprising.

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