Multi-stage vacuum pump

Abstract

A multi-stage vacuum pump is described that includes a stator defining multiple pumping chambers. The stator includes multiple transfer channels that provide a fluid passage from an outlet port of one of the multiple pumping chambers to an inlet port of a subsequent pumping chamber. Some of the transfer channels include two side channel portions on opposite sides of the stator. One of the transfer channels includes a single side channel portion on one side of the stator. The vacuum pump further includes a gas ballast inlet channel disposed on the opposite side of the stator relative to one side of the stator.

Description

[Technical field]

[0001] The field of the invention relates to multi-stage vacuum pumps. [Background technology]

[0002] Multi-stage vacuum pumps require transfer channels to transport fluid between stages as it is pumped from the inlet to the outlet of the vacuum pump. These transfer channels require space within the stator block. Also, if additional access to the chambers is required, such as for adding gas ballast to one or more stages, these additional channels and / or valves must be provided, which can be difficult, especially in small, compact pumps. Summary of the Invention [Problem to be solved by the invention]

[0003] Embodiments seek to provide a compact multi-stage pump with a gas ballast inlet channel for supplying ballast gas to one of the pump stages. [Means for solving the problem]

[0004] A first aspect is a multi-stage vacuum pump, a stator defining a plurality of pumping chambers; the stator includes a plurality of transfer channels each providing a fluid passage from an outlet port of one of the pumping chambers to an inlet port of a subsequent pumping chamber; At least one of the transfer channels includes two side channel portions on either side of the stator; At least one of the transfer channels includes a single side channel portion on one side of the stator; The vacuum pump further comprises a gas ballast inlet channel disposed on an opposite side of the stator relative to the one side of the stator, providing a multi-stage vacuum pump.

[0005] The inventors of the present invention have recognized that in multi-stage vacuum pumps, especially compact multi-stage vacuum pumps, there is limited space within the stator for the pumping chambers and for the transfer channels directing fluid between the pumping chambers of different stages. In this regard, the transfer channels should be sized such that their cross-sections are large enough to allow gas flow between the chambers without significant pressure loss.

[0006] When a vacuum pump pumps from high vacuum to low vacuum, the volume of gas pumped at the inlet end is significantly larger than the volume pumped at the outlet end, and therefore the pumping chamber and transfer channel can also decrease in size from inlet to outlet.

[0007] In some pumps, it may be advantageous to provide a gas ballast inlet channel for introducing ballast gas into the vacuum pump during certain stages of the pumping cycle to inhibit condensation of pumped condensable gases, such as water vapor. The ballast gas can be air or an inert gas or a process gas, and this flow helps to "dilute" the vapors in the pump mechanism and inhibit condensation, for example, of water vapor when compressed to near atmospheric pressure. This allows the pump to recover to its final pressure much faster than without the use of a gas ballast. The gas ballast also allows more vapor to be pumped than without the use of a gas ballast, since it helps inhibit condensation in the pump.

[0008] These gas ballast inlet channels are generally located towards the exhaust end of the vacuum pump because condensation of gas occurs at this end. The inventors have recognized that the volume of gas pumped towards the exhaust side of the vacuum pump is generally small, and therefore there is an opportunity to locate the ballast gas inlet channel in the stator of the vacuum pump. In particular, the inventors have recognized that in order to provide a transfer channel of sufficient size to not impede the flow, these transfer channels are generally formed in two lateral parts on either side of the pumping chamber in the side wall of the stator, with linking channels between the inlet and the outlet, and in some cases a single lateral part can be used for one of the transfer channels on only one side of the stator, in which case there is available space on the other side of the stator where the other lateral channel would conventionally be. In such a case, the gas ballast channel can be located in the free space on this side provided by not providing a second lateral part for one of the transfer channels. Thus, by adapting the transfer channel configuration in the stator, a gas ballast channel can be provided in the stator for supplying gas ballast to one of the pumping chambers in the vacuum pump without having to increase the size of the stator or the vacuum pump.

[0009] In some embodiments, at least some of the portions of the transfer channel providing a fluid passage between pumping chambers closer to the vacuum pump inlet have a cross-section that is larger than a cross-section of the portions of the transfer channel between pumping chambers closer to the pump outlet.

[0010] As mentioned above, when gas is pumped through a vacuum pump, it is compressed and therefore the volume occupied by the gas is reduced. Therefore, the cross section of the transport channel required for relatively unrestrained fluid flow is smaller at the outlet of the vacuum pump than at the inlet. Thus, in some embodiments, it is possible to take advantage of the fact that the size of at least some of the transport channels between the pumping chambers decreases from the inlet to the outlet, and the size required to provide the same pressure loss is significantly larger at the inlet than at the outlet. Reducing the size of the transport channels is an effective way to efficiently use the space in the stator.

[0011] In some embodiments, the transport channel including the single side channel portion has a cross-section that is larger than a cross-section of an adjacent upstream transport channel.

[0012] On the other hand, if a transport channel only has a single side channel portion due to the arrangement of a gas ballast channel on the opposite side of the stator, this side channel can have a larger cross section than the channel portion in the presence of two side channels, since the amount of gas flowing through this side channel is twice as much as when two side channels are present, and in this case, this transport channel does not have a reduced cross-sectional area compared to the cross-sectional area of ​​the side channel portion of the immediately preceding upstream transport channel.

[0013] In some embodiments, the stator includes side walls on either side of the multiple pumping chambers and a cover portion covering opposing sides of the multiple pumping chambers, the inlet and outlet ports of the multiple pumping chambers respectively extending toward the inlet and outlet cover portions, and the cover portion includes portions of the transfer channel connecting the respective inlets and outlets to the side channel portions.

[0014] The transfer channel provides a passageway for fluid to flow from the outlet of one pumping chamber to the inlet of a subsequent pumping chamber and may include one or more side channel portions extending perpendicular to the cover portion through one or both side walls of the stator and connecting channels connecting opposite ends of the side channel portions to the respective inlets and outlets. The connecting channels are provided in the surfaces covering the pumping chambers at the respective inlet and outlet ends.

[0015] In some embodiments, the stator comprises a clamshell stator including two clamshell components, the side channel portion and pumping chamber extending into both clamshell components, one of the clamshells including an inlet clam including an inlet portion of the pumping chamber and the other of the clamshells including an outlet clam including an outlet portion of the pumping chamber.

[0016] In some embodiments, the stator is formed as a two-block clamshell stator to facilitate mounting of the rotor within the stator.

[0017] In some embodiments, the channel connecting the pumping chamber inlet to the single side channel of the inlet cover portion is angled, the single side channel portion is offset relative to the pumping chamber inlet to which it is connected via the connecting channel, and the side channel is closer to the vacuum pump inlet than the pumping chamber inlet.

[0018] As mentioned above, there is limited space for providing a transport channel within the stator, and a transport channel with a single side channel can have a larger cross-section; to provide this space, it can be advantageous to angle the channel so that the side channel is offset relative to the pumping chamber.

[0019] In some embodiments, the transfer channel adjacent to the channel including the single side channel and closer to the vacuum pump inlet includes an angled connecting portion in the inlet cover portion, the side channel portion being offset with respect to the pumping chamber inlet to which it is connected via the connecting channel, and the side channel portion being closer to the vacuum pump inlet than the pumping chamber inlet.

[0020] To provide additional space for the gas ballast inlet, it may be advantageous to also angle the next transfer channel connecting portion towards the inlet, thereby providing additional space for both the wider cross-sectional side portion for the transfer channel with a single side portion and the connecting channel portion, as well as the gas ballast inlet channel.

[0021] A single side channel can connect between any two of the pumping chambers, but in some embodiments the transfer channel including the single side channel portion is a channel connecting the third-to-last pumping chamber to the second-to-last pumping chamber, which is adjacent to the exhaust pumping chamber.

[0022] As mentioned above, the gas ballast is advantageously introduced into the vacuum pump towards the exhaust end of the vacuum pump, and therefore the gas ballast channel may be advantageously located in the stator towards the exhaust side of the vacuum pump, in particular in the space vacated by the side channel connecting the penultimate pumping chamber to the penultimate pumping chamber.

[0023] In some embodiments, a portion of the gas ballast inlet channel is disposed at least partially on the opposite side of the stator to one side of the penultimate pumping chamber.

[0024] When a transfer channel including a single side channel portion connects between the third-to-last pumping chamber and the second-to-last pumping chamber, the gas ballast inlet channel can be positioned at least partially within the space on one side of the third-to-last pumping chamber vacated by the absence of a side channel to the transfer channel at this point.

[0025] In some embodiments, the gas ballast inlet channel includes a cavity that includes a check valve that restricts flow from the pump to the gas ballast inlet port.

[0026] It is advantageous to arrange a check valve in the gas ballast inlet channel so that the gas pumped by the vacuum pump does not escape through this channel when the pressure in the pumping chamber rises. This check valve is advantageously close to the pumping chamber to avoid the buffering effect of any volume between the check valve and the pumping chamber, which is therefore a further reason why it is advantageous for the gas ballast channel to be arranged close to the pumping chamber to which the gas is delivered. The check valve is arranged in a cavity in the channel and therefore requires a considerable volume.

[0027] In some embodiments, the gas ballast inlet channel includes a control valve for admitting gas ballast through the gas ballast inlet channel or for sealing the pumping chamber from the gas ballast.

[0028] To control the introduction of gas ballast into the vacuum pump, a control valve may be provided to allow the introduction of gas ballast when and as much as is required for the particular stage at which the pump is being processed.

[0029] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims as appropriate and in combinations other than those explicitly set out in the claims.

[0030] Where a feature of an apparatus is described as providing a functionality, this feature should be understood to include a feature of the apparatus that provides that functionality or that is adapted or configured to provide that functionality.

[0031] Hereinafter, embodiments of the present invention will be further described with reference to the accompanying drawings. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is an isometric view of the main stator components of a vacuum pump according to the prior art. [Diagram 2] FIG. 2 is a top view of the inlet stator component of FIG. 1. [Diagram 3] FIG. 2 is a top view of an inlet stator component according to an embodiment. [Figure 4] FIG. 2 is an end view of a stator inlet component according to an embodiment. [Diagram 5] FIG. 2 illustrates an isometric view of a stator inlet component according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Before describing the embodiments in more detail, an overview will first be provided.

[0034] An embodiment provides a multi-stage vacuum pump including a stator at least partially surrounding a plurality of vacuum chambers, the stator including transfer channels for transferring fluid between the plurality of pumping chambers from an outlet of one pumping chamber to an inlet of a subsequent pumping chamber, the transfer channels being disposed within the stator.

[0035] In some embodiments, the stator includes sidewalls between which the pumping chambers and rotor are disposed, and cover portions extending perpendicular to the sidewalls and covering the upper and lower surfaces of one or more stator components including the chambers. These cover portions can be separate plates or can be part of a stator block that includes the sidewalls.

[0036] In some embodiments, a portion of the transfer channel has two side channel portions that penetrate the side wall of the stator and are disposed at least partially on either side of each pumping chamber. The inlets of the multiple pumping chambers extend toward the inlet cover portion and the outlets extend toward the opposing outlet cover portion. The transfer channel is configured to direct fluid from the outlet of one pumping chamber along a connecting channel in the outlet cover portion toward the side channel portion, where the fluid flows through the side channel portion into the channel in the inlet cover portion where it is directed to the inlet of the subsequent pumping chamber.

[0037] The cross-sectional area of ​​the fluid transfer channels is preferably large enough so as not to unduly impede flow.

[0038] As the fluid flows from the inlet to the outlet of the vacuum pump it is compressed, thus reducing the cross-sectional area required for the fluid and allowing the cross-section of the transport channel to be reduced as well.

[0039] An embodiment provides a gas ballast inlet channel for supplying gas ballast to one of the pumping chambers in the vacuum pump for evacuation purposes, and in order to provide space for such a gas ballast inlet channel, one of the transfer channels between the pumping chambers is configured to have only a single lateral portion on one side of the stator leaving the opposite side of the stator available for the gas ballast channel, the single lateral portion of the transfer channel having an increased cross-sectional area compared to at least one of the adjacent upstream transfer channels to provide sufficient conducting force for gas flow in the one channel.

[0040] Figure 1 shows a vacuum pump stator according to the prior art, comprising an inlet half-shell stator component 2 and an outlet half-shell stator component 4, which together form the body of a stator block. In this example, the stator is for a five-stage vacuum pump and comprises five pumping chambers separated by partition members in the form of horizontal walls. These horizontal walls are preferably integral with the stator components 2 and 4.

[0041] The stators are provided with apertures 34 and 36, each for receiving a respective shaft of a rotor assembly of the vacuum pump. In this embodiment, the vacuum pump comprises a Roots vacuum pump and the rotor comprises a Roots rotor. Attached to end faces 38 and 40 of the stator components 2,4 are head plates (not shown) that seal the ends of the stator components 2,4.

[0042] Each pumping chamber includes an inlet that is connected to a channel at the top surface of component 2. The transfer channel between the inlet and outlet of each of the pumping chambers has lateral portions that extend vertically through blocks 2 and 4 at either end of the pumping chamber, which lateral portions extend into the channel shown at the top surface to provide passage of gas from the lateral channel portions to the inlet of the pumping chamber.

[0043] The pumping chamber outlets open into channels (not shown) in the underside of the outlet stator component 4, and in this surface there are connecting channels providing passage from the pumping chamber outlets to the respective side channels.

[0044] FIG. 2 shows a top surface 52 of an inlet stator component 2 according to the prior art. In this view, the inlets 17, 19, 21, 23 and 25 of the respective pumping chambers are shown. Also present in the surface of this inlet stator component 2 are connecting channels that connect the inlets to the respective side channel portions of the transfer channels on both sides of the stator. On the left side, the openings of the side channel portions are shown as 12, 14, 16, 18, 20, which are connected to the respective inlets of the pumping chambers by connecting channels that run along the surface 52 of the inlet stator portion. Similarly, on the right side, the openings of the side channel portions are shown as 22, 24, 26, 28 and 30, which are also connected to the inlets via connecting channels. In this prior art vacuum pump, there are side channel portions of the transfer channels on both sides of the pumping chambers for each pumping chamber, with the cross section of the side channel portions decreasing from the inlet side 60 to the outlet side 62 of the vacuum pump. The side channel is disposed on one side of the pumping chamber such that the connecting channel in the inlet stator portion extends perpendicular to the side wall.

[0045] 3 is an end view of the top surface 52 of the inlet stator component 2 according to one embodiment. Although there are seven pumping chambers in this multi-stage pump, five pumping chamber inlets are shown in this component, with the inlet stage being in the inlet head plate (not shown) and the outlet stage being below a groove that contains a seal that surrounds the stator component and is therefore not visible in FIG.

[0046] In Fig. 3 the inlet 17 to the second pumping chamber and the subsequent inlets 19, 21, 23 and 25 are shown, while a further inlet 27 to the exhaust pump stage is shown in Fig. 4. Between the stages of the multi-stage vacuum pump there are transfer channels for transferring fluids, each of which has a side portion that penetrates the side of the stator at least partially adjacent to the pumping chamber. In the second pumping chamber with the inlet 17 there are two side channel portions on either side that provide sufficient flow for the low pressure gas. These two side channel portions are shown as 12 on the left and 22 on the right. The subsequent pumping chamber has a side channel portion 14 on the left and a side channel portion 24 on the right. These side channels are arranged to receive fluid from the outlet of the previous pumping chamber present on the opposite face of the other stator component 4, the fluid flows through the channels to the inlet face and then along the connecting channels 14a and 24a to the inlet 19.

[0047] The fluid is then pumped through the pumping chamber and output at the outlet of the outlet face of the stator component 4 into the subsequent side channels 16 and 26, before moving to the inlet face 52 of the inlet component 2 and from there through a connecting channel into the inlet 21 of the subsequent pumping chamber.

[0048] In this embodiment, a gas ballast inlet channel 70 is provided for inputting ballast gas into the exhaust stage of the vacuum pump. In this embodiment, the gas ballast inlet channel 70 is located on one side of the penultimate pumping chamber with inlet 25. This penultimate pumping chamber receives fluid from a transfer channel that has only one side portion 30, which transfers fluid from the penultimate pumping chamber to the penultimate pumping chamber. This transfer channel has a larger cross-sectional area than the phase channel that transfers fluid between the previous two pumping chambers, since there is only one side channel portion. This results in space for the gas ballast inlet channel 70 on the other side of the stator.

[0049] Towards the exhaust end of the vacuum pump, the cross-sectional area required for the transfer channels becomes smaller, so increasing the cross-sectional area of ​​the side portions of the transfer channels does not overtax space. However, space is limited, so in this embodiment the side channels 30 are offset relative to the pumping chamber and pumping chamber inlet 25, so that the connecting channels 30a are angled. This allows the channels to be larger, yet still provides space for subsequent side channels to the next exhaust stage that do not open onto the surface 52 but run across below the surface, as shown in FIG.

[0050] 4 is an end view of the inlet stator component 2 with the pumping chamber inlet 27 to the exhaust pumping chamber. The gas ballast inlet passage 70 opens into a connecting linking channel 31a that connects a lateral portion of the left-hand transfer channel 31 from the penultimate to the exhaust stage to the inlet 27 of the exhaust pumping stage. Thus, both the gas ballast and the fluid from the penultimate pumping chamber flow through the connecting channel 31a to the inlet 27. There is also a further connecting channel 32a that connects a lateral portion of the right-hand transfer channel 32 to the inlet of the exhaust pumping chamber.

[0051] Figure 5 is an isometric view of the inlet stator component 2. It shows the gas ballast inlet channels 70 with their openings on the top surface of the component, as well as the connecting channels that connect the side portions of the transport channels to the inlet. The side channels extend downward from these connecting channels and are not visible. The end view is visible, showing how the inlet 27 is connected to the exhaust stage by its own connecting channel.

[0052] Gas flow through the vertical side channels is in an upward direction as shown, from the outlets of the respective pumping chambers on the lower surface of the stator outlet block 4 through the transfer channels to the upper surface of the inlet stator block. The gas ballast channels receive ballast gas from openings in the upper surface 52 of the inlet clam, which flows down to the inlet of the exhaust stage.

[0053] The gas ballast channel has a check valve (not shown) located in the channel close to the exhaust pumping chamber to restrict the flow of gas from the pumping chamber to the ballast gas inlet port, and a control valve (also not shown) to control the input of ballast gas.

[0054] Although exemplary embodiments of the present invention are disclosed in detail herein with reference to the accompanying drawings, it is understood that the present invention is not limited to the precise embodiments, and that those skilled in the art can make various changes and modifications in the embodiments without departing from the scope of the present invention defined by the appended claims and their equivalents. [Explanation of symbols]

[0055] 2 Inlet Half-Shell Stator Components 4 Outlet Half Shell Stator Components 17, 19, 21, 23, 25, 27 Pumping chamber inlet 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 31, 32 Transfer channel side parts 14a, 24a, 30a, 31a, 32a Transfer channel connecting portion 34, 36 Rotor accommodation aperture 38, 40 End face of stator block 52 Top surface of inlet half-shell stator component 60 Vacuum inlet end 62 Vacuum pump outlet end 70 Gas ballast inlet channel

Claims

1. A multi-stage vacuum pump, a stator defining a plurality of pumping chambers; the stator includes a plurality of transfer channels each providing a fluid passage from an outlet port of one of the pumping chambers to an inlet port of a subsequent pumping chamber; At least one of the transfer channels includes two side channel portions on either side of the stator; At least one of the transfer channels includes a single side channel portion on one side of the stator; the vacuum pump further comprising a gas ballast inlet channel disposed on an opposite side of the stator relative to the one side of the stator. A multi-stage vacuum pump.

2. a cross-section of at least some of the portions of the transfer channel providing a fluid passage between the pumping chambers closer to the vacuum pump inlet has a larger cross-section than a cross-section of the portions of the transfer channel between the pumping chambers closer to the outlet port; 2. A multi-stage vacuum pump according to claim 1.

3. the transport channel including the single side channel portion has a cross-section larger than a cross-section of an adjacent upstream transport channel; 3. A multi-stage vacuum pump according to claim 1 or 2.

4. the stator includes side walls on either side of the plurality of pumping chambers and a cover portion covering opposing sides of the plurality of pumping chambers, the inlet and outlet ports of the plurality of pumping chambers respectively extending toward the inlet and outlet cover portions, the cover portion including portions of the transfer channel connecting the respective inlets and outlets to the side channel portions; 4. A multi-stage vacuum pump according to claim 1.

5. the stator comprises a clamshell stator including two clamshell components, the side channel portion and the pumping chamber extending into both of the clamshell components, one of the clamshell components including an inlet clam including an inlet portion of the pumping chamber and the other of the clamshell components including an outlet clam including an outlet portion of the pumping chamber; 5. A multi-stage vacuum pump according to claim 1.

6. a channel connecting the pumping chamber inlet to the single side channel of the inlet cover portion is angled, the single side channel portion being offset relative to the pumping chamber inlet to which it is connected via a connecting channel, the side channel being closer to the vacuum pump inlet than the pumping chamber inlet; 6. A multi-stage vacuum pump according to claim 4 or 5.

7. the transfer channel adjacent to the channel including the single side channel and proximate the vacuum pump inlet includes an angled connecting portion in an inlet cover portion, the side channel portion being offset with respect to the pumping chamber inlet to which it is connected via a connecting channel, the side channel portion being closer to the vacuum pump inlet than the pumping chamber inlet; 6. A multi-stage vacuum pump according to claim 4 or 5.

8. the transfer channel including the single side channel portion is a channel connecting a third-to-last pumping chamber to a second-to-last pumping chamber, the second-to-last pumping chamber being adjacent to an exhaust pumping chamber; A multi-stage vacuum pump according to any one of claims 1 to 7.

9. a portion of the gas ballast inlet channel is disposed at least partially on the opposite side of the stator to the one side of the third-to-last pumping chamber; 9. A multi-stage vacuum pump according to claim 8.

10. the gas ballast inlet channel includes a cavity containing a check valve that inhibits flow from the pump to the gas ballast inlet port. A multi-stage vacuum pump according to any one of claims 1 to 9.

11. the gas ballast inlet channel includes a control valve for admitting gas ballast through the gas ballast inlet channel or for sealing the pumping chamber from the gas ballast; A multi-stage vacuum pump according to any one of claims 1 to 10.

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