EP4684133A1

EP4684133A1 - Scroll pump

Info

Publication number: EP4684133A1
Application number: EP24716445.2A
Authority: EP
Inventors: Alan Ernest Kinnaird Holbrook; Nigel Paul Schofield; Edward Peter JEPSON; David Bedwell; Nicolas Jonathan GRANT
Original assignee: Edwards Ltd
Current assignee: Edwards Ltd
Priority date: 2023-03-23
Filing date: 2024-03-22
Publication date: 2026-01-28
Also published as: GB202304245D0; JP2026509548A; CN120835959A; WO2024194653A1

Abstract

A scroll pump 10' includes an inlet (28), an outlet, and two scroll members comprising a fixed scroll (12) and an orbiting scroll (14) interleaving with the fixed scroll (12) and mounted such that rotation of a motor imparts an orbital motion to the orbiting scroll (14) relative to the fixed scroll (12). Each scroll member has a base (16, 20) from which an involute wall (18, 22) extends to define a pumping chamber for conveying fluid from the inlet (28) to the outlet and which, with orbital movement of the orbiting scroll (14), transitions from an open configuration, in which the pumping chamber receives fluid from the inlet along a first flow path, to a closed configuration, in which the pumping chamber is isolated from the inlet. A base of one of the scroll members includes a channel (34) in fluid communication with the inlet and positioned so that, when the pumping chamber is in an open configuration, the pumping chamber receives fluid from the inlet along an additional flow path passing through the channel (34).

Description

SCROLL PUMP FIELD OF THE INVENTION The field of the invention relates to scroll pumps. Example embodiments relate to scroll pumps with increased inlet conductance. BACKGROUND Scroll pumps comprise interleaving fixed and orbiting scrolls that are mounted for relative orbital motion. Bases and involute walls of the scrolls define pumping chambers which convey fluid from an inlet of the pump to an outlet of the pump. The inlet is typically located on a peripheral portion of the scroll pump. For example, the inlet may be located in a peripheral portion of the fixed scroll. The outlet is typically located in a central portion of the pump. For example, the outlet may be in the form of a port located centrally in a base of one of the scroll members. A pumping chamber can adopt an open configuration in which it receives fluid from the inlet along a flow path. With orbital movement of the orbiting scroll relative to the fixed scroll, the pumping chamber becomes increasingly isolated from the inlet until it adopts a closed configuration in which it is substantially fully isolated from the inlet. With further orbital movement, the closed pumping chamber moves towards the outlet along a spiral path, becoming increasingly smaller in size to compress fluid trapped within the pumping chamber. Eventually, the pumping chamber comes into fluid communication with the outlet to enable the compressed fluid to be emitted from the pumping chamber. When in an open configuration, fluid may enter the pumping chamber from the inlet through an open end of the pumping chamber, located between the involute wall of the fixed scroll and the involute wall of the orbiting scroll. The flow path for fluid entering the pumping chamber from the inlet thus extends substantially parallel to the bases of the scroll members. The pumping chambers of scroll pumps tend to have very high aspect ratios. In other words, the pumping chamber is relatively long whereas its width and height are relatively short, meaning that the open end of the pumping chamber tends to have a relatively small cross-sectional area. This can present a restriction to the fluid flow into the pumping chamber, and thus the inlet conductance of the pump, which can be a limiting factor to the pumping capacity of the pump. It would be desirable to be able to increase the inlet conductance of a scroll pump. SUMMARY The present invention provides a scroll pump comprising: an inlet for receiving fluid to be pumped; an outlet for conveying pumped fluid from the scroll pump; and two scroll members comprising a fixed scroll and an orbiting scroll interleaving with the fixed scroll and mounted such that rotation of a motor imparts an orbital motion to the orbiting scroll relative to the fixed scroll, each of the scroll members comprising a base from which an involute wall extends to define a pumping chamber for conveying fluid from the inlet to the outlet and which, with orbital movement of the orbiting scroll, transitions from an open configuration, in which the pumping chamber receives fluid from the inlet along a first flow path, to a closed configuration, in which the pumping chamber is substantially isolated from the inlet; wherein a base of one of the scroll members includes a channel in fluid communication with the inlet and positioned so that, when the pumping chamber is in an open configuration, the pumping chamber receives fluid from the inlet along an additional flow path passing through the channel. This channel defines, at least in part, an additional flow path for fluid to enter the pumping chamber when it is in an open configuration, and thus can increase the inlet conductance of the pump. The inlet preferably extends through a circumferential outer wall of the fixed scroll. The first fluid flow path is preferably arranged to convey fluid from the inlet and into the pumping chamber between the involute wall of the fixed scroll and one end of the involute wall of the orbiting scroll. The first fluid flow path preferably extends substantially parallel to the bases of the scroll members. The area of an opening between the involute walls of the scroll members, through which fluid passing along the first flow path enters the pumping chamber, decreases as the pumping chamber moves towards a closed configuration, and thus the rate of fluid flow along the first flow path varies as the relative positions of the scroll members changes. The channel is preferably located adjacent to the inlet of the scroll pump. This enables the additional flow path to be a relatively short path for the incoming fluid. Were the channel to be located remote from the inlet, a longer fluid flow path might be required, and this would have a reduced conductance. The channel is preferably elongate in shape in order to maximise the area through which fluid passing along the additional flow path can enter the pumping chamber, and preferably extends partially about the axis of orbital movement of the orbiting scroll relative to the fixed scroll. This can increase the extent of orbital movement in which the channel is in fluid communication with the pumping chamber. The channel preferably extends around this axis by an angle in the range from 10 to 60 degrees, preferably in the range from 15 to 30 degrees. The channel is arranged such that the additional flow path conveys fluid into the pumping chamber between the involute walls of the scroll members, and preferably in a direction which is substantially orthogonal to the bases of the scroll members. Thus, the area of the channel through which fluid passing along the additional flow path enters the pumping chamber also decreases as the pumping chamber moves towards its closed configuration, and thus the rate of fluid flow along the additional flow path also varies as the relative positions of the scroll members changes. The direction in which fluid enters the pumping chamber from the channel is preferably substantially orthogonal to the direction in which fluid enters the pumping chamber directly from the inlet. The channel is preferably shaped such that the channel is in fluid communication with the pumping chamber when it is in an open configuration and is substantially isolated from the pumping chamber when it is in a closed configuration. The channel may be positioned such that open fluid communication between the channel and the pumping chamber is synchronized with open fluid communication between the inlet and the pumping chamber. In this way an additional fluid flow path is provided into the pumping chamber when in its open configuration thereby increasing inlet conductance without unduly negatively affecting the pumping capability of the scroll pump. Preferably, the channel is fully isolated from the pumping chamber when it is in its closed configuration, that is, when, at both ends of the pumping chamber, there is a minimum, or no, separation between the involute wall of the fixed scroll and the involute wall of the orbiting scroll. It should be noted that although the scroll pump may have such synchronisation between the open fluid communication between the channel and the pumping chamber and the open fluid communication between the inlet and the pumping chamber, a slight delay in this synchronization can still provide an effective, improved pump. For example, the channel may become isolated from the pumping chamber before the pumping chamber becomes fully isolated from the inlet. The channel may be provided in the base of the fixed scroll. Alternatively, the channel may be provided in the base of the orbiting scroll. In this latter case, relative orbital motion of the scroll members moves the channel relative to the fixed scroll. This can allow the orbital motion to move the channel from a first position when the pumping chamber inlet is in a fully open configuration, that is, when there is a maximum separation between the involute wall of the fixed scroll and the end wall of the involute wall of the orbiting scroll defining the pumping chamber, where substantially the whole channel allows fluid to enter the pumping chamber along the additional flow path, to a second position when the pumping chamber inlet is in a closed configuration where substantially no fluid enters the pumping chamber along the additional flow path. As a further alternative, a first said channel may be located in the base of the fixed scroll and a second said channel may be located in the base of the orbiting scroll. This can enable a second additional flow path to be established between the inlet and the pumping chamber when it is in an open configuration, and thus further improve conductance. The channel may be configured to be at least partially obscured from the pumping chamber when the pumping chamber is in an open configuration. The extent to which the channel is obscured from the pumping chamber preferably varies as the relative positions of the scroll members changes. The channel may convey fluid from the inlet into an outermost pumping chamber of the scroll pump. For example, the channel may be provided on the base of the fixed scroll and adjacent to an outer circumferential wall of the fixed scroll. This wall may be a wall of a housing of the scroll pump. Alternatively, the channel may be provided on an outer flange of the base of the orbiting scroll. The scroll pump may have several pumping chambers. For example, there may be one on either side of the involute wall of the orbiting scroll. Each of these two pumping chambers may be in an open configuration simultaneously so that each receives fluid along two respective flow paths, one conveying fluid from the inlet directly into the pumping chamber and the other conveying fluid from the inlet into the pumping chamber via the channel. When one of these two pumping chambers is in a closed configuration, the other of these two pumping chambers is preferably in a fully open configuration. In some embodiments, the channel may move across the intervening involute wall with relative orbital movement between the scroll members. The channel may be segmented along its length by strips extending from one side to another. This can provide support for tip seals provided on the end of the involute wall facing the channel. The scroll pump may have a plurality of said channels to increase fluid conductance to respective pumping chambers. The scroll pump may comprise a multi-start scroll pump comprising a plurality of inlets, said scroll pump comprising a plurality of said channels each located adjacent a respective inlet. The scroll pump may be in the form of a scroll vacuum pump. Orbiting scroll refers to the scroll that orbits during use of the scroll. It will be appreciated that the orbiting scroll will itself be stationary when the pump is not in use. BRIEF DESCRIPTION OF THE DRAWINGS Preferred features of the present invention will now be described further, with reference to the accompanying drawings, in which: Figure 1 schematically shows a top sectional view of an inlet portion of a known scroll pump; Figure 2 is a side sectional view taken along line A-A in Figure 1; Figure 3 schematically shows a top sectional view of an inlet portion of an embodiment of a scroll pump; Figure 4 is a side sectional view taken along line B-B in Figure 3; and Figures 5 to 8 show the inlet portion of the scroll pump of Figure 3 at different points in an orbital cycle of the pump. DETAILED DESCRIPTION OF THE DRAWINGS Figures 1 and 2 illustrate schematic sectional views of an inlet portion of a conventional scroll pump 10. The scroll pump 10 comprises two scroll members in the form of a fixed scroll 12 and an orbiting scroll 14 which is driven by a motor (not shown) to orbit relative to the fixed scroll 12 about an orbiting axis which is offset from the centre of the fixed scroll 12. The fixed scroll 12 comprises a base 16 and an involute, or spiral, wall 18 which is upstanding from and orthogonal to the base 16. Similarly, the orbiting scroll 14 comprises a base 20 and an involute, or spiral, wall 22 which is upstanding from and orthogonal to the base 22. The bases 16, 18 and the involute walls 20, 22 of the scroll members, together with a peripheral outer wall 24 of the fixed scroll 12, define a plurality of pumping chambers, indicated generally at 26, therebetween. Depending on the relative positions of the fixed scroll 12 and the orbiting scroll 14, the pumping chambers 26 are arranged to adopt either an open configuration, in which the pumping chamber is in fluid communication with an inlet 28 of the scroll pump 10, and a closed configuration, in which the pumping chamber is isolated from the inlet 28. The inlet 28 extends through the outer wall 24 of the fixed scroll 12. With the relative positions of the fixed scroll 12 and the orbiting scroll 14 as illustrated in Figure 1, a first pumping chamber 30 and a second pumping chamber 32 are in an open configuration so that fluid can enter the first pumping chamber 30 from the inlet 28 along a first flow path, indicated generally at F1, and fluid can enter the second pumping chamber 32 from the inlet 28 along a second flow path, indicated generally at F2. Each of the first flow path F1 and second flow path F2 extend parallel to the bases 16, 18 of the scroll members. As the orbiting scroll 14 moves in an orbital movement relative to the fixed scroll 12, each of the first pumping chamber 30 and the second pumping chamber 32 will, in turn, move to a closed configuration in which the pumping chamber is isolated from the inlet 28. With further orbital movement, the closed pumping chambers move inwardly towards a central outlet (not shown) of the scroll pump 10 along a spiral path, becoming increasingly smaller in size to compress fluid trapped within the pumping chambers. Eventually, each pumping chamber comes into fluid communication with the outlet to enable the compressed fluid to be emitted from the scroll pump 10. When the first pumping chamber 30 is in an open configuration, fluid enters the first pumping chamber 30 through an open end of the first pumping chamber 30, located between the involute wall 18 of the fixed scroll 12 and the involute wall 22 of the orbiting scroll 14. When the second pumping chamber 32 is in an open configuration, fluid enters the second pumping chamber 32 through an open end of the second pumping chamber 32, located between the outer wall 24 of the fixed scroll 12 and the involute wall 22 of the orbiting scroll 14. The open ends of the pumping chambers tend to have relatively small cross-sectional areas. This can present a restriction to the fluid flow into the pumping chambers. Figures 3 and 4 illustrate schematic sectional views of an inlet portion of an embodiment of a scroll pump 10’. Features of the scroll pump 10’ which are identical to that of the scroll pump 10 have been indicated using the same reference numerals and will not be described again here. The scroll pump10’ differs from the scroll pump 10 in that base 16 of the fixed scroll 12 comprises a channel 34 in the form of a cutaway formed in the base 16. The channel 34 is in fluid communication with the inlet 28. The channel 34 is located adjacent to the inlet 28 and extends lengthways partially about the axis about which the orbiting scroll 14 moves relative to the fixed scroll 12. As described in more detail below, the channel 34 is positioned in the fixed scroll 12 so that an additional flow path F3 can be established between the inlet 28 and a pumping chamber in an open configuration. With reference to Figure 4, in the illustrated relative positions of the fixed scroll 12 and the orbiting scroll 14 the additional flow path F3 extending from the inlet 28 to the first pumping chamber 30 via the channel 34. Fluid enters the first pumping chamber 30 from the channel 34 in a direction which is orthogonal to the bases 16, 20 of the scroll members, and parallel to the longitudinal axis of the scroll pump 10’. Thus, fluid enters the first pumping chamber 30 from the channel 34 (along additional flow path F3) in a direction which is orthogonal to the direction in which fluid enters the first pumping chamber 30 directly from the inlet 28 (along first flow path F1). Positioning the channel 34 adjacent to the inlet 28 can minimise the length of the additional flow path F3 and thus further improve the conductance of the scroll pump 10’. Figures 5 to 8 illustrate how the first pumping chamber 30 becomes isolated from the channel 34 as that pumping chamber moves towards a closed configuration in which it is isolated from the inlet 28. In these figures, the orbiting scroll 14 is illustrated in a series of different positions relative to the fixed scroll 12, as would occur during the orbital movement of the orbiting scroll 14 relative to the fixed scroll 12 during use of the scroll pump 10’. In the position of the orbiting scroll 14 illustrated in Figure 5, the first pumping chamber 30 is in a fully open configuration, in which the radial distance between the end 36 of the involute wall 22 of the orbiting scroll and the involute wall 18 of the fixed scroll 12 is at a maximum. In this position, the area of the outlet 38 of the channel 34 which is in fluid communication with the first pumping chamber 30 is also at a maximum. A first portion of the fluid entering the scroll pump 10’ passes from the inlet 28 into the first pumping chamber 30 along the first flow path F1, whereas a second portion of the fluid entering the scroll pump 10’ passes from the inlet 28 into the first pumping chamber 30 along the additional flow path F3. In this position of the orbiting scroll, the radially outermost pumping chamber 40 is in a closed configuration and isolated from both the inlet 28 and the channel 34 by the involute wall 22 of the orbiting scroll 14. Figure 6 illustrates the position of the orbiting scroll 14 relative to the fixed scroll 12 following a 30 degree orbital movement of the orbiting scroll 14 from the position illustrated in Figure 5. A second pumping chamber 32 has been established between the involute wall 22 of the orbiting scroll 14 and the outer wall 24 of the fixed scroll 12. Both the first pumping chamber 30 and the second pumping chamber 32 are in an open configuration. The first pumping chamber 30 remains in fluid communication with the inlet 28 via the first flow path F1 and the additional flow path F3, although the sizes of both of these flow paths have decreased in view of the movement of the orbiting scroll 14 relative to the fixed scroll. The second pumping chamber 32 is in fluid communication with the inlet 28 via the second flow path F2. Figure 7 illustrates the position of the orbiting scroll 14 relative to the fixed scroll 12 following a 90 degree orbital movement of the orbiting scroll 14 from the position illustrated in Figure 6. The first pumping chamber 30 remains in an open configuration but it has become substantially isolated from the channel 34 by the involute wall 22 of the orbiting scroll 14 so that fluid enters the first pumping chamber 30 substantially via only the first flow path F1 (although there may be some leakage of fluid into the first pumping chamber 30 from the channel 34 from beneath the involute wall 22). On the other hand, the second pumping chamber 32 remains in an open configuration but fluid now enters the second pumping chamber via both the second flow path F2 and the additional flow path F3. Figure 8 illustrates the position of the orbiting scroll 14 relative to the fixed scroll 12 following a 30 degree orbital movement of the orbiting scroll 14 from the position illustrated in Figure 7. The first pumping chamber 30 is in a closed configuration in which it is fully isolated from the inlet 28 by the involute wall 22 of the orbiting scroll 14. The second pumping chamber 32 remains in an open configuration but with an increased amount of fluid entering the second pumping chamber via both the second flow path F2 and the additional flow path F3. Thus, in this embodiment, the first pumping chamber 30 has transitioned from a fully open configuration to a closed configuration following an orbital movement of the orbiting scroll 14 relative to the fixed scroll 12 of 150 degrees. REFERENCE SIGNS 10 scroll pump 10’ scroll pump 12 fixed scroll 14 orbiting scroll 16 base 18 involute wall 20 base 22 involute wall 24 outer wall 26 pumping chambers 28 inlet 30 first pumping chamber 32 second pumping chamber 34 channel 36 end of involute wall 38 channel outlet 40 outermost pumping chamber F1 first flow path F2 second flow path F3 additional flow path

Claims

CLAIMS 1. A scroll pump comprising: an inlet for receiving fluid to be pumped; an outlet for conveying pumped fluid from the scroll pump; and two scroll members comprising a fixed scroll and an orbiting scroll interleaving with the fixed scroll and mounted such that rotation of a motor imparts an orbital motion to the orbiting scroll relative to the fixed scroll, each of said scroll members comprising a base from which an involute wall extends to define a pumping chamber for conveying fluid from the inlet to the outlet and which, with orbital movement of the orbiting scroll, transitions from an open configuration, in which the pumping chamber receives fluid from the inlet along a first flow path, to a closed configuration, in which the pumping chamber is substantially isolated from the inlet; wherein a base of one of the scroll members includes a channel in fluid communication with the inlet and positioned so that, when the pumping chamber is in an open configuration, the pumping chamber receives fluid from the inlet along an additional flow path passing through the channel.

2. A scroll pump according to claim 1, wherein first fluid flow path is arranged to convey fluid from the inlet and into the pumping chamber between the involute wall of the fixed scroll and one end of the involute wall of the orbiting scroll.

3. A scroll pump according to claim 1 or claim 2, wherein the first fluid flow path extends substantially parallel to the bases of the scroll members.

4. A scroll pump according to any preceding claim, wherein the channel is located adjacent to the inlet.

5. A scroll pump according to any preceding claim, wherein the channel is elongate in shape and extends lengthways partially about the axis of orbital movement of the orbiting scroll relative to the fixed scroll.

6. A scroll pump according to claim 5, wherein the channel extends around said axis by an angle in the range from 10 to 60 degrees, preferably in the range from 15 to 30 degrees.

7. A scroll pump according to any preceding claim, wherein the additional flow path is arranged to convey fluid into the pumping chamber in a direction which is substantially orthogonal to the bases of the scroll members.

8. A scroll pump according to any preceding claim, wherein the direction in which fluid enters the pumping chamber from the channel is substantially orthogonal to the direction in which fluid enters the pumping chamber directly from the inlet.

9. A scroll pump according to any preceding claim, wherein the channel is shaped such that the channel is in fluid communication with the pumping chamber when it is in an open configuration and is substantially isolated from the pumping chamber when it is in a closed configuration.

10. A scroll pump according to any preceding claim, comprising a plurality of pumping chambers, and wherein the channel is arranged to convey fluid from the inlet into an outermost pumping chamber.

11. A scroll pump according to any preceding claim, wherein the channel is arranged to convey fluid simultaneously into two pumping chambers, each of which is in an open configuration.

12. A scroll pump according to claim 11, wherein the channel is arranged to convey fluid into only one of the two pumping chambers when the other pumping chamber is in a closed position.

13. A scroll pump according to any preceding claim, wherein the channel is located in the base of the fixed scroll.

14. A scroll pump according to any of claims 1 to 12, wherein the channel is located in the base of the orbiting scroll.

15. A scroll pump according to any of claims 1 to 12, comprising a first said channel in the base of the fixed scroll and a second said channel located in the base of the orbiting scroll.