MULTI-STAGE DISPENSING VACUUM PUMP

Description

TECHNICAL FIELD

[0001] The present invention relates to a multi-stage positive displacement vacuum pump.BACKGROUND

[0002] Certain vacuum systems, such as mass spectrometry systems, may comprise multiple vacuum chambers. The pressure is reduced in stages through consecutive chambers. Each chamber communicates with adjacent chambers via a restriction and requires individual pumping to provide the required vacuum. The pumping of these systems is conventionally performed using a plurality of pumps, one or more pumps for each chamber. There may be a high vacuum pump, such as a turbomolecular pump, for pumping the highest vacuum chamber, while lower vacuum chamber(s) are pumped by other lower vacuum pumps, such as a scroll or Roots pump. The turbo pump is a secondary pump and as such is itself backed by a pump such as a scroll pump.

[0003] A multi-stage vacuum pump 103 is schematically shown in Figure 9. The vacuum pump 103 comprises seven stages 172. The stages of the vacuum pump 103 progressively decrease in size as the pressure within the vacuum pump 103 increases. The vacuum pump 103 comprises a fluid input inlet 113 connected to an inlet stage 112; and an exhaust 117 connected to an outlet stage 172. The fluid is input at the fluid input inlet 113 at a relatively low pressure and pumped through each of the stages in series and output at the exhaust 117 at atmospheric pressure. The fluid is pumped through each of the stages in sequence, as illustrated by the flow arrows shown in Figure 9.

[0004] GB 2 558 626 A discloses a multi-stage vacuum pump with a gas flow diverter and a bypass gas flow path for conducting a flow of gas diverted from an output of an intermediate one of the stages to the exhaust, to increase power consumption and thus the temperature of the pump.

[0005] It would be desirable to provide a cost and space efficient pump that would be suitable for differentially pumping multiple chambers.SUMMARY OF THE INVENTION

[0006] According to the present invention there is provided a multi-stage positive displacement vacuum pump as per claim 1.

[0007] The multi-stage positive displacement vacuum pump comprising a pump housing having; a first stator component and a second stator component, for defining a plurality of pumping chambers, a first fluid input inlet, for conveying fluid into a first one of the plurality of pumping chambers; and a second fluid input inlet, for conveying fluid into a second one of the plurality of pumping chambers; the first stator component comprising a plurality of fluid inlet channels for conveying fluid to respective pumping chambers, each fluid inlet channel having an inlet port for conveying fluid into the pumping chamber; the second stator component comprising a plurality of fluid outlet channels, for conveying pumped fluid from respective pumping chambers, each fluid outlet channel having an outlet port for receiving pumped fluid from the pumping chamber; the first stator component and the second stator component defining a plurality of fluid transfer channels, each for conveying fluid from a respective one of the fluid outlet channels to a respective one of the fluid inlet channels, each fluid transfer channel having an inlet for receiving pumped fluid and an outlet for conveying pumped fluid; a diversion channel for diverting pumped fluid from a first one of the outlet channels to the outlet channel of said second one of the plurality of pumping chambers; wherein the first stator component is adapted to receive at least one sealing member for inhibiting the conveyance of pumped fluid into the second one of the pumping chambers or the second stator component is adapted to receive at least one sealing member for inhibiting conveyance of pumped fluid through the fluid transfer channel outlet of the fluid transfer channel for conveying fluid to the second one of the pumping chambers.

[0008] In use, the at least one sealing member may cooperate with the first stator component to form a substantially fluid-tight seal. The sealing member thereby inhibits the conveyance of fluid into the pumping chamber. The conveyance of fluid through the pump is thereby modified. The stator component is for a multi-stage positive displacement pump. The pump may, for example, be a Roots, claw or screw pump. The stator component has particular application in a multi-stage vacuum pump.

[0009] The first stator component may comprise a seat for receiving the sealing member. The seat may be configured to cooperate with the sealing member to form a substantially fluid-tight seal. The sealing member may form the substantially fluid-tight seal when seated in the seat. The seat may comprise a sealing surface for cooperating with the sealing member. The sealing surface may be substantially planar. Sealing means, such as a gasket or a sealant, may optionally be provided between the sealing member and the seat.

[0010] The seat may extend at least partway around the inlet port or the fluid transfer channel inlet. For example, the seat may comprise or consist of a ring-shaped sealing surface extending at least partway around the inlet port or the fluid transfer channel inlet.

[0011] The seat may comprise a recess. At least a portion of the sealing member may locate in the recess to form the substantially fluid-tight seal. The sealing surface may be formed on the recess.

[0012] Each stator component may comprise a half-shell stator component. The pump housing may comprise a first half-shell stator component for fastening to a second half-shell stator component. The first and second half-shell stator components form the plurality of pumping chambers. The first half-shell stator component may be an upper component in the pump housing; and the second half-shell stator component may be a lower component in the pump housing. The first half-shell stator component may be mounted on top of the second half-shell stator component.

[0013] The sealing member may be removable, for example to enable the pump to be configured in a plurality of operating modes. Alternatively, the sealing member may be fastened in place.

[0014] The sealing member may at least substantially seal the fluid transfer channel to inhibit the conveyance of fluid to the fluid inlet channel. The sealing member may be disposed at or proximal to an inlet or an outlet of the fluid transfer channel. The sealing member may optionally be disposed at or proximal to the fluid transfer channel inlet. The sealing member may be disposed between the first and second half-shell stator components. The sealing member may comprise a sealing plate. The sealing plate may locate in a seat formed at the fluid transfer channel inlet or at the fluid transfer channel outlet. The seat may be recessed.

[0015] The stator assembly may comprise fastening means for fastening the sealing member in position. The fastening means may comprise one or mechanical fastener; or an adhesive fastener. The sealing member may be a restriction fit in the fluid transfer channel.

[0016] The sealing member may at least substantially seal the inlet port to inhibit the conveyance of fluid to the pumping chamber. The sealing member may comprise a sealing plate for sealing the inlet port.

[0017] The sealing member may comprise an insert for closing the fluid inlet channel. The insert may extend across the fluid inlet channel to form the seal.

[0018] The sealing member may comprise a fluid input inlet for admitting fluid to the pumping chamber from an external fluid source. The fluid input inlet may comprise an inlet port. The external fluid source may be distinct from the fluid transfer channel and the fluid inlet channel.

[0019] The stator assembly may comprise a cover plate fastened to the first stator component. The cover plate may define a sidewall of the fluid inlet channels. For example, the fluid inlet channels formed in the first stator component may be open channels which are closed by the cover plate. The sealing member may be provided on the cover plate. The sealing member may be mounted to the cover plate. Alternatively, the sealing member may be formed integrally with the cover plate.

[0020] In a variant, the cover plate and the sealing member may be separate from each other. The cover plate and the sealing member may cooperate with each other to form the seal. The cover plate may retain the sealing member in position.

[0021] The seat may be formed in the first stator component by performing a machining operation, such as drilling and or milling.

[0022] The diversion channel may be formed using one or more machining operations, such as drilling and / or milling.

[0023] In the assembled pump housing, each outlet channel may be associated with a respective one of the pumping chambers.

[0024] The references to the first one of the outlet channels and the second one of the outlet channels are not intended to infer a particular sequence or proximity of the outlet channels or the associated pumping chambers in relation to each other. The outlet channels may be adjacent to each other. For example, the first one of the outlet channels may be associated with a first pumping chamber and the second one of the outlet channels may be associated with a second pumping chamber. In this arrangement, the diversion channel may be configured to bypass the second pumping chamber. Alternatively, the outlet channels may be spaced apart (separated) from each other. For example, one or more intermediate outlet channels may be disposed between the first one of the outlet channels and the second one of the outlet channels. In this arrangement, the diversion channel may be configured to bypass the or each of the intermediate pumping chambers.

[0025] The pump may comprise a first control valve for controlling the supply of fluid to the first fluid input inlet; and a second control valve for controlling the supply of fluid to the second fluid input inlet.

[0026] The first and second control valves may be controllable independently of each other. The pump may be configurable to operate with the first control valve open and the second control valve closed. Conversely, the pump may be configurable to operate with the second control valve open and the first control valve closed.

[0027] The references to the first one of the pumping chambers and the second one of the pumping chambers are not intended to infer a particular sequence or proximity of the pumping chambers in relation to each other. The pumping chambers may be adjacent to each other or may be spaced apart from each other. For example, one or more intermediate pumping chambers may be disposed between the first one of the pumping chambers and the second one of the pumping chambers.

[0028] A pump control unit may be provided for controlling operation of the first and second control valves. The pump control unit may comprise a controller, for example comprising at least one electronic processor and a memory device.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a schematic representation of a multi-stage vacuum pump in accordance with an embodiment of the present invention; Figure 2 shows a perspective view of a stator assembly comprising first and second stator components of the multi-stage vacuum pump shown in Figure 1; Figure 3 shows an enlarged view of the first stator component and a recess for receiving a sealing member to seal the inlet port; Figure 4 shows a perspective view of an underside of a cover plate incorporating a sealing member to locate in the seat shown in Figure 3; Figure 5 shows an end view of the cover plate shown in Figure 4; Figure 6 shows a variant of the first stator component incorporating a separate sealing member to seal the inlet port; Figures 7 and 8 shows a further variant of the first stator component incorporating a sealing plate to seal the fluid transfer channel; and Figure 9 shows a known multi-stage vacuum pump. DETAILED DESCRIPTION

[0030] A pump housing 1 in accordance with an embodiment of the present invention is described herein with reference to the accompanying figures. A pump 3 comprising the pump housing 1 is shown in Figure 1. The pump 3 may, for example, be a Roots pump. The pump 3 is a multi-stage positive displacement pump. In the present embodiment, the pump 3 is a multi-stage positive displacement vacuum pump.

[0031] The pump housing 1 comprises a first stator component 5, a second stator component 7 and a cover plate 9. As shown in Figure 2, the first stator component 5 and the second stator component 7 form a stator assembly of the pump housing 1. In the present embodiment, the first and second stator components 5, 7 are respective first and second half-shell stator components. The first stator component 5 is mounted on top of the second stator component 7. As shown in Figure 1, the cover plate 9 is mounted on an upper surface of the first stator component 5. The first and second stator components 5, 7 and the cover plate 9 are assembled using mechanical fasteners, such as bolts. The first and second stator components 5, 7 are machined, cast or otherwise formed.

[0032] The first and second stator components 5, 7 define a plurality of pumping chambers 11-n in the pump housing 1. The pumping chambers 11-n each form a stage of the pump 3. The pump 3 in the present embodiment has seven (7) pumping chambers 11-1, 11-2, 11-3, ...11-7 corresponding to seven (7) stages. In particular, the pump 3 comprises a first stage 12, a second stage 22, a third stage 32, a fourth stage 42, a fifth stage 52, a sixth stage 62 and a seventh stage 72. The stages of the pump 3 are referenced herein in relation to their position within the pump housing 1. The sizes of the pumping chambers 11-n in the pump 3 progressively decrease; the first pumping chamber 11-1 having the largest volume and the seventh pumping chamber 11-7 having the smallest volume. The pump housing 1 comprises a first fluid input inlet 13 connected to the first stage 12; a second fluid input inlet 15 connected to the second stage 22; and an exhaust 17 connected to the seventh stage 72. First and second external fluid sources are connected to the first and second fluid input inlets 13, 15 respectively. In use, the first and second external fluid sources supply first and second fluid flows. As described herein, the fluid pumped through the pump 3 does not necessarily pass through all of the stages 12, 22, 32, 42, 52, 62, 72 of the pump 3. Furthermore, the fluid is not necessarily pumped through each of the stages 12, 22, 32, 42, 52, 62, 72 in sequence. In a variant, the second fluid input inlet 15 may be connected to one of the other intermediate stages 32, 42, 52, 62.

[0033] The pump 3 in the present embodiment effectively utilises the seven stages as two six-stage pumps. The first six-stage pumps, pumps fluid from the first fluid input inlet 13 via the first stage 12 through the third stage 32, the fourth stage 42, the fifth stage 52, the sixth stage 62 and the seventh stage 72 to exhaust 30. The second six-stage pump introduces fluid through the second fluid input inlet 15 via the second stage 22, through the third stage 32, the fourth stage 42, the fifth stage 52, the sixth stage 62 and the seventh stage 72 to exhaust 30. Thus, in the present embodiment the third stage 32, the fourth stage 42, the fifth stage 52, the sixth stage 62 and the seventh stage 72 are shared by fluid input from each of the first and second fluid input inlets 13, 15. The first stage 12 pumps fluid exclusively input from the first fluid input inlet 13; and the second stage 22 pumps fluid exclusively input from the second fluid input inlet 15.

[0034] The first stator component 5 comprises a plurality of fluid inlet channels 19-n, the fluid inlet channels 19-n each being associated with one of the pumping chambers 11-n. The fluid inlet channels 19-n each comprise an inlet port 21-n for conveying fluid into the associated pumping chambers 11-n. As shown in Figure 2, the inlet channels 19-n are open on the top (as illustrated) external surface 23 of the first stator component 5. The second stator component 7 comprises a plurality of fluid outlet channels 25-n through which pumped fluid is exhausted. The fluid outlet channels 25-n each have an outlet port (not shown) for exhausting fluid from an associated one of the pumping chambers 11-n. The outlet ports are open on the bottom (as illustrated) external surface 29 of the second stator component 7.

[0035] The first and second stator components 5, 7 define fluid transfer channels 31-n for conveying fluid between the pumping chambers 11-n. In particular, the fluid transfer channels 31-n are configured to convey fluid from the fluid outlet channels 25-n to respective fluid inlet channels 19-n. A first fluid transfer channel 31-1 is arranged to convey fluid from the first outlet channel 25-1 (shown in dashed lines in Figure 1) of the first pumping chamber 11-1 to the second inlet channel 19-2 of the second pumping chamber 11-2. A second fluid transfer channel 31-2 is arranged to convey fluid from the second outlet channel 25-2 of the second pumping chamber 11-2 to the third inlet channel 19-3 of the third pumping chamber 11-3. This pattern is repeated for each of the pumping chambers 11-n such that, in use, fluid is pumped from the first pumping chamber 11-1 to the seventh pumping chamber 11-7 through each of the intermediate pumping chambers 11-n in sequence.

[0036] Each fluid transfer channel 31-n is formed in both the first stator component 5 and the second stator component 7. A first (upper) section of the fluid transfer channel 31-n is formed in the first stator component 5 to convey fluid to the inlet channel 19-n. A second (lower) section of the fluid transfer channel 31-n is formed in the second stator component 7 to convey fluid from the outlet channel 25-n. The first section of the fluid transfer channel 31-n has a transfer channel inlet 33-n for receiving fluid from a transfer channel outlet formed in the second section of the fluid transfer channel 33-n. In the present embodiment, the inlet fluid transfer channels 31-n extend substantially orthogonal to the top and bottom external surfaces 23, 29 to facilitate manufacture and cleaning.

[0037] The inlet channels 19-n are shaped to convey fluid from the transfer channels 31-n into respective pumping chambers 11-n. The fluid is introduced into the pumping chambers 11-n from the inlet channels 19-n via the inlet ports 21-n. In the present embodiment, each inlet channel 19-n extends in a transverse direction across a substantial part of the width of the pump housing 1. The inlet channels 19-n are in the form of one or more slots (or grooves) formed in the top external surface 23 of the first stator component 5. As shown in Figure 2, the first and inlet channels 19-1, 19-2 in the present embodiment each comprise a pair of slots separated by an intermediate wall. The cover plate 9 is fastened to the first stator component 5 to close the open top portion of the slots. The second inlet port 21-2 for conveying fluid into the second pumping chamber 11-2 is shown in Figure 3.

[0038] The outlet channels 25-n are shaped to convey pumped fluid from the outlet ports to respective transfer channels 31-n. The pumped fluid is exhausted from the pumping chambers 11-n through the outlet ports and into the outlet channels 25-n. The outlet channels 25-n may be inclined at an acute angle to a longitudinal axis of the pump housing 1 for conveying pumped fluid to the transfer channel 31-n associated with the next pumping chamber 11-n. Alternatively, or in addition, the transfer channels 31-n may be inclined at an acute angle to the longitudinal axis of the pump housing 1.

[0039] As outlined above, first and second fluid flows are connected to the first and second fluid input inlets 13, 15. The first fluid input inlet 13 is configured to admit fluid into the first pumping chamber 11-1 from a first external fluid source; and the second fluid input inlet 15 is configured to admit fluid into the second pumping chamber 11-2 from a second external fluid source. The pump 3 in the present embodiment comprises first and second control valves 37, 39 for selectively controlling the supply of fluid to the first and second fluid input inlets 13, 15. The first and second control valves 37, 39 can be controlled independently of each other. A controller may be provided for controlling the first and second control valves 37, 39.

[0040] A diversion channel (or bypass duct) 41 is provided for diverting pumped fluid from the first outlet channel 25-1 to the second outlet channel 25-2. The diversion channel 41 bypasses the first transfer channel 31-1, effectively bypassing the second pumping chamber 11-2. The diversion channel 41 in the present embodiment is formed in the second stator component 7. The diversion channel 41 may, for example, comprise an aperture or a conduit for establishing a fluid pathway between the first and second outlet channels 25-1, 25-2. The fluid is diverted from the first outlet channel 25-1 to the second outlet channel 25-2 and admitted into the second transfer channel 31-2. In a variant, the diversion channel 41 may be configured to convey fluid from the first pumping chamber 11-1 to one of the other pumping chambers 11-n. For example, the diversion channel 41 could be configured to connect the first outlet channel 25-1 with the third outlet channel 25-3.

[0041] The pump housing 1 comprises a sealing member 43 (shown in Figure 1) for inhibiting the conveyance of fluid from the first pumping chamber 11-1 to the second pumping chamber 11-2 via the first transfer channel 31-1. In the present embodiment, the sealing member 43 is configured at least substantially to seal the second inlet port 21-2 through which fluid is conveyed into the second pumping chamber 11-2. The sealing member 43 is in the form of an insert which extends around the perimeter of the second inlet port 21-2. As shown in Figure 3, the first stator component 5 comprises a seat 45 for cooperating with the sealing member 43 to form the seal. The seat 45 in the present embodiment comprises a recess for receiving a portion of the sealing member 43. The seat 45 defines a sealing surface 47 for cooperating with the sealing member 43. The sealing member 43 thereby forms a seal operative to inhibit the conveyance of fluid through the second inlet port 21-2. In the present embodiment, the sealing member 43 is formed integrally with the cover plate 9. The sealing member 43 is fastened in position when the pump housing 1 is assembled. By forming the sealing member 43 and the cover plate 9 integrally, the sealing member 43 cannot be omitted when the pump housing 1 is assembled. In a variant, the sealing member 43 may be a separate component, for example mounted to the cover plate 9. The pump housing 1 may comprise sealing means, such as a sealant or a gasket, to enhance the seal established by the sealing member 43.

[0042] The sealing member 43 in the present embodiment also forms the second fluid input inlet 15 to admit fluid into the second pumping chamber 11-2 from the second external fluid source. As shown in Figures 4 and 5, the second fluid input inlet 15 comprises an inlet aperture 49 extending through the cover plate 9. The cover plate 9 comprises a connector 51 for connecting the second external fluid source. In the present embodiment, the connector 51 is formed integrally with the cover plate 9. The inlet aperture 49 extends through the connector 51. The connector 51 comprises one or more fasteners (not shown) for connecting the second external fluid source.

[0043] The pump housing 1 is assembled by mounting the first stator component 5 on the second stator component 7 to form the pumping chambers 11-n. The cover plate 9 is fastened to the first stator component 5. The sealing member 43 locates in the seat 45 and seals the second inlet port 21-2. The sealing member 43 forms the second fluid input inlet 15 for receiving fluid from a second external source.

[0044] The operation of the pump 3 will now be described. A first fluid flow is supplied to the first pumping chamber 11-1 via the first fluid input inlet 13. A second fluid flow is supplied to the second pumping chamber 11-1 via the second fluid input inlet 15. The first and second control valves 37, 39 are actuated to control the supply of the first and second fluids. The first and second control valves 37, 39 can be opened simultaneously such that the first and second fluid flows are provided simultaneous to the pump 3. In the present embodiment, the first and second fluids can be mixed within the third pumping chamber 11-3. In a variant, one of the first and second control valves 37, 39 can be opened and the other one of the first and second control valves 37, 39 can be closed. This enables the pump 3 to be configured selectively to pump one of the first and second fluids. The pump 3 is configured to differentially pump multiple chambers. The first inlet 13 configured to connect to a lower vacuum chamber and the second inlet 15 is configured to act as a backing pump for a vacuum pump pumping a higher vacuum chamber. The pump 3 is configured to pump at a higher gas flow rate through the first inlet 13 than through the second inlet 15. The pump 3 is configured to pump a gas flow rate through the first inlet 13 that may be greater than ten (10) times higher than the gas flow rate through the second inlet 15.

[0045] In the above embodiment the sealing member 43 is disposed on the cover plate 9. In a variant, the sealing member 43 may be a separate component which locates in the second fluid inlet channel 19-2 to seal the second inlet port 21-2. This variant is illustrated in Figure 6. The cover plate 9 is mounted to the first stator component 5, thereby retaining the sealing member 43 in position.

[0046] A further embodiment of the pump housing 1 will now be described with reference to Figures 7 and 8. Like reference numerals are used for like components. The description herein will focus on the differences over the previous embodiment.

[0047] The pump housing 1 described with reference to Figures 1 to 6, comprises a sealing member 43 for sealing the second inlet port 21-2. In the present embodiment, the sealing member 43 is configured to seal the first transfer channel 31-1. As shown in Figure 7, the sealing member 43 comprises a sealing plate which is mounted in the transfer channel inlet 33-1. The sealing member 43 is thereby disposed at the interface between the first and second stator components 5, 7. The first stator component 5 comprises a seat 45 for receiving the sealing plate. The seat 45 comprises a recess formed in a lower face of the first stator component 5. The sealing member 43 is fixed in position when the first stator component 5 is fastened to the second stator component 7.

[0048] It will be understood that this embodiment may be modified by forming the seat 45 in the second stator component 5. For example, the seat 45 may be formed in the upper face of the second stator component 7.

[0049] A separate connector 51 may be provided for connecting the second external fluid source to the second pumping chamber 11-2. The connector 51 may, for example, be open to the second inlet channel 19-2.

[0050] As outlined above, the first and second stator components 5, 7 may be formed using appropriate techniques, such as machining and / or casting. According to a further aspect of the present invention there is provided a method of converting a first stator component (5) and / or a second stator component (7) of a prior art pump housing (1) to implement at least some of the features described herein.

[0051] An embodiment of the present invention may relate to a method of converting a first stator component (5) comprising a plurality of fluid inlet channels (19-n) for conveying fluid to respective pumping chambers (11-n), and a plurality of fluid transfer channels (31-n) for conveying fluid to a respective one of the fluid inlet channels (19-n). The conversion process may comprise forming a seat (45) in the stator component (5) for receiving at least one sealing member (43) to inhibit the conveyance of fluid into an associated one of the pumping chambers (11-n). As described herein, the seat (45) may comprise or consist of a ring-shaped sealing surface (47) extending at least partway around an inlet port (21-n) of one of the fluid inlet channels (19-n). Alternatively, or in addition, the seat (45) may comprise or consist of a ring-shaped sealing surface (47) extending at least partway around one of the fluid transfer channel inlets (33-n). The seat (45) may be formed by forming a recess in the stator component (5), for example by milling a surface of the first stator component (5). The seat (45) may comprise or consist of a substantially planar surface.

[0052] An embodiment of the present invention may relate to a method of converting a second stator component (7) comprising a plurality of fluid outlet channels (25-n) for conveying fluid from pumping chambers (11-n), and a plurality of fluid transfer channels (31-n) for conveying pumped fluid from the fluid outlet channels (25-n). The method may comprise forming a diversion channel (41) in the stator component (5) for diverting pumped fluid from a first one of the outlet channels (25-n) to a second one of the outlet channels (25-n). The diversion channel (41) may be formed using one or more machining operations, such as drilling and / or milling. As described herein, the outlet channels (25-n) are associated with respective pumping chambers (11-n) in the assembled pump housing. The first one of the outlet channels (25-n) may be associated with a first pumping chamber (11-1) and the second one of the outlet channels (25-n) may be associated with a second pumping chamber (11-2). In this arrangement, the diversion channel (41) may be configured to bypass the second pumping chamber (11-2). Alternatively, the outlet channels (25-n) may be spaced apart from each other. For example, one or more intermediate outlet channels (25-n) may be disposed between the first one of the outlet channels (25-n) and the second one of the outlet channels (25-n). In this arrangement, the diversion channel (41) may be configured to bypass the or each intermediate pumping chamber (11-n).

[0053] It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the invention as defined in the appended claims. Reference Numeral Component 1Pump housing3Pump5First stator component7Second stator component9Cover plate11-nPumping chambers12, 22, 32, 42, 52, 62, 72Pump stages13First fluid input inlet15Second fluid input inlet17Exhaust19-nFluid inlet channel21-nInlet port (for pumping chamber)23Top external surface25-nFluid outlet channel27-nOutlet port (from pumping chamber)29-nBottom external surface31-nFluid transfer channel33-nTransfer channel inlet37First control valve39Second control valve41Diversion channel (bypass duct)43Sealing member45Seat47Sealing surface49Inlet aperture51Connector

Claims

1. A multi-stage positive displacement vacuum pump (3), comprising a pump housing (1) having; a first stator component (5) and a second stator component (7), for defining a plurality of pumping chambers (11-n), a first fluid input inlet (13), for conveying fluid into a first one of the plurality of pumping chambers (11-n); and a second fluid input inlet (15), for conveying fluid into a second one of the plurality of pumping chambers (11-n); the first stator component (5) comprising a plurality of fluid inlet channels (19-n) for conveying fluid to respective pumping chambers (11-n), each fluid inlet channel (19-n) having an inlet port (21-n) for conveying fluid into the pumping chamber (11-n); the second stator component (7) comprising a plurality of fluid outlet channels (25-n), for conveying pumped fluid from respective pumping chambers (11-n), each fluid outlet channel (25-n) having an outlet port (27-n) for receiving pumped fluid from the pumping chamber (11-n); the first stator component (5) and the second stator component (7) defining a plurality of fluid transfer channels (31-n), each for conveying fluid from a respective one of the fluid outlet channels (25-n) to a respective one of the fluid inlet channels (19-n), each fluid transfer channel (31-n) having an inlet (33-n) for receiving pumped fluid and an outlet for conveying pumped fluid; a diversion channel (41) for diverting pumped fluid from a first one of the outlet channels to the outlet channel of said second one of the plurality of pumping chambers (11-n); wherein the first stator component (5) is adapted to receive at least one sealing member (43) for inhibiting the conveyance of pumped fluid into the second one of the pumping chambers (11-n) or the second stator component (7) is adapted to receive at least one sealing member (43) for inhibiting conveyance of pumped fluid through the fluid transfer channel outlet of the fluid transfer channel for conveying fluid to the second one of the pumping chambers.

2. A multi-stage positive displacement vacuum pump (3) as claimed in claim 1 wherein the first stator component (5) comprises a seat (45) for receiving the sealing member (43) to form a fluid-tight seal.

3. A multi-stage positive displacement vacuum pump (3) as claimed in claim 2, wherein the seat (45) comprises or consists of a ring-shaped sealing surface (47) extending at least partway around the inlet port (21-n) or the fluid transfer channel inlet (33-n).

4. A multi-stage positive displacement vacuum pump (3) as claimed in claim 2 or claim 3, wherein the seat (45) comprises a recess.

5. A multi-stage positive displacement vacuum pump (3) as claimed in any one of the preceding claims, wherein the first stator component (5) and the second stator component (7) are half-shell stator components, the first half-shell stator component (5) for fastening to the second half-shell stator component (7).

6. A multi-stage positive displacement vacuum pump (3) as claimed in any one of the preceding claims, wherein the sealing member (43) and the first stator component (5) cooperate with each other to inhibit the conveyance of pumped fluid to the second one of the pumping chambers (11-n).

7. A multi-stage positive displacement vacuum pump (3) as claimed in claim 6, wherein the sealing member (43) seals the fluid transfer channel (31-n) for conveying fluid to the second one of the pumping chambers to inhibit the conveyance of pumped fluid to the fluid inlet channel (19-n) for conveying fluid to the second one of the pumping chambers, the sealing member (43) optionally being disposed at the fluid transfer channel inlet (33-n) of the fluid transfer channel (31-n) for conveying fluid to the second one of the pumping chambers.

8. A multi-stage positive displacement vacuum pump (3) as claimed in claim 6, wherein the sealing member (43) seals the inlet port (21-n) for conveying fluid to the second one of the pumping chambers to inhibit the conveyance of pumped fluid to the second one of the pumping chambers (11-n), wherein the sealing member (43) comprises the second fluid input inlet (15) for admitting fluid to the second one of the pumping chambers (11-n) from an external fluid source.

9. A multi-stage positive displacement vacuum pump (3) as claimed in any one of claims 6 to 8 comprising a cover plate (9) fastened to the first stator component (5), wherein the sealing member (43) is disposed on the cover plate (9), wherein the sealing member (43) is optionally formed integrally with the cover plate (9).

10. A multi-stage positive displacement vacuum pump (3) as claimed in claim 9, wherein the cover plate (9) comprises a fluid inlet (49) for admitting fluid to the second one of the pumping chambers (11-n) from an external fluid source.