Scroll pump

Abstract

The scroll pump (10 ') comprises an inlet (28), an outlet and two scroll members including a fixed scroll (12) and an orbiting scroll (14) interlaced with the fixed scroll (12), the scroll members being mounted such that rotation of the motor imparts an orbiting 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 an inlet (28) to an outlet and 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 receives fluid from the outlet along a second flow path, with an orbiting movement about the orbiting scroll (14). In the closed configuration, the pumping chamber is isolated from the inlet. The base of one of the scroll members includes a channel (34) in fluid communication with the inlet and positioned such that when the pumping chamber is in the open configuration, the pumping chamber receives fluid from the inlet along an additional flow path through the channel (34).

Description

TECHNICAL FIELD

[0001] The field of the invention relates to scroll pumps. Exemplary embodiments relate to scroll pumps having increased inlet flow conductance. BACKGROUND

[0002] Scroll pumps comprise interleaved fixed and orbiting scroll plates which are mounted for relative orbiting movement. The bases and involute walls of the scroll plates define pumping chambers which convey fluid from an inlet of the pump to an outlet of the pump. The inlet is typically located on an outer peripheral portion of the scroll pump. For example, the inlet can be located in an outer peripheral portion of the fixed scroll plate. The outlet is typically located on a central portion of the pump. For example, the outlet can be in the form of a port centrally located in the base of one of the scroll members.

[0003] The pumping chamber can adopt an open configuration in which it receives fluid from the inlet along a flow path. As the orbiting scroll plate orbits relative to the fixed scroll plate, the pumping chamber progressively isolates from the inlet until it adopts a closed configuration in which it is substantially completely isolated from the inlet. As further orbiting movement occurs, the closed pumping chamber moves along a spiral path towards the outlet, thereby becoming progressively smaller in size to compress fluid trapped within the pumping chamber. Eventually, the pumping chamber fluidly communicates with the outlet to enable compressed fluid to be expelled from the pumping chamber.

[0004] When in the open configuration, fluid can enter the pumping chamber from the inlet through an open end of the pumping chamber which is located between the involute wall of the fixed scroll plate and the involute wall of the orbiting scroll plate. The flow path for fluid to enter the pumping chamber from the inlet therefore extends substantially parallel to the bases of the scroll members.

[0005] The pumping chambers of scroll pumps tend to have a very high aspect ratio. In other words, the pumping chambers are relatively long, while their width and height are relatively short, which means that the open end of the pumping chamber tends to have a relatively small cross-sectional area. This imposes a restriction on the flow of fluid into the pumping chamber, and therefore on the inlet flow conductance of the pump, which can be a limiting factor on the pumping capacity of the pump.

[0006] It can be desirable to be able to increase the inlet flow conductance of a scroll pump. SUMMARY

[0007] The 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 including a stationary scroll and an orbiting scroll interleaved with the stationary scroll and mounted such that rotation of a motor imparts an orbiting motion to the orbiting scroll relative to the stationary scroll, each of the scroll members including a base from which an involute wall extends to define a pumping chamber for conveying fluid from the inlet to the outlet, and as the orbiting motion of the orbiting scroll, the pumping chamber 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 the base of one of the scroll members includes a channel that is in fluid communication with the inlet and positioned such that when the pumping chamber is in the open configuration, the pumping chamber receives fluid from the inlet along an additional flow path through the channel.

[0008] The channel at least partially defines the additional flow path for fluid to enter the pumping chamber when the pumping chamber is in the open configuration, and thus can increase the inlet flow conductance of the pump.

[0009] The inlet preferably extends through a circumferential outer wall of the stationary 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 stationary scroll and one end of the involute wall of the orbiting scroll. The first fluid flow path preferably extends substantially parallel to the base of the scroll members. As the pumping chamber moves towards the closed configuration, the area of the opening between the involute walls of the scroll members decreases, and fluid passing along the first flow path through the opening into the pumping chamber, so the rate of fluid flow along the first flow path varies as the relative positions of the scroll members change.

[0010] The channel is preferably positioned adjacent to the inlet of the scroll pump. This enables the additional flow path to be a relatively short path for fluid to enter. If the channel were positioned away from the inlet, a longer fluid flow path can be required, and this would have a reduced flow conductance.

[0011] The channel is preferably elongate in shape so as to maximise the area through which fluid passing along the additional flow path can enter the pumping chamber, and preferably extends partially around an axis of the orbiting motion of the orbiting scroll relative to the stationary scroll. This can increase the extent of the orbiting motion in which the channel is in fluid communication with the pumping chamber. The channel preferably extends around the axis through an angle in the range 10 to 60 degrees, preferably in the range 15 to 30 degrees.

[0012] The passage is arranged such that the additional flow path delivers fluid into the pumping chamber between the involute walls of the scroll member and preferably in a direction substantially normal to the base of the scroll member. Thus, as the pumping chamber moves towards its closed configuration, the area of the passage through which fluid passing along the additional flow path enters the pumping chamber also decreases and thus the rate of fluid flow along the additional flow path also varies as the relative position of the scroll member changes.

[0013] The direction in which fluid enters the pumping chamber from the passage is preferably substantially normal to the direction in which fluid enters the pumping chamber directly from the inlet.

[0014] The passage is preferably shaped such that it is in fluid communication with the pumping chamber when the pumping chamber is in an open configuration and substantially isolated from the pumping chamber when the pumping chamber is in a closed configuration. The passage can be positioned such that the open fluid communication between the passage and the pumping chamber is synchronised with the open fluid communication between the inlet and the pumping chamber. In this way, when the pumping chamber is in its open configuration, an additional fluid flow path is provided into the pumping chamber, thereby increasing the inlet flow conductance, without undue negative impact on the pumping capacity of the scroll pump.

[0015] Preferably, the passage is completely isolated from the pumping chamber when the pumping chamber is in its closed configuration, i.e. when the spacing between the involute walls of the fixed scroll and the involute walls of the orbiting scroll at both ends of the pumping chamber is minimal or non-existent. It should be noted that although the scroll pump can have this synchronisation between the open fluid communication between the passage and the pumping chamber and the open fluid communication between the inlet and the pumping chamber, a slight delay in this synchronisation can still provide an effective, improved pump. For example, the passage can be isolated from the pumping chamber before the pumping chamber is completely isolated from the inlet.

[0016] The passage can be provided in the base of the fixed scroll. Alternatively, the passage can be provided in the base of the orbiting scroll. In the latter case, the relative orbiting motion of the scroll members moves the passage relative to the fixed scroll. This can allow the orbiting motion to move the passage from a first position when the pumping chamber inlet is in a fully open configuration, i.e. when there is a maximum spacing between the involute walls of the fixed scroll and the end walls of the orbiting scroll defining the involute walls of the pumping chamber, in which substantially the entire passage 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 in which substantially no fluid enters the pumping chamber along the additional flow path.

[0017] As a further alternative, the first said channel can be located in the base of the fixed scroll and the second said channel can be located in the base of the orbiting scroll. This can result in the establishment of a second additional flow path between the inlet and the pumping chamber when the pumping chamber is in the open configuration and thus further improve the flow conductance.

[0018] The channel can be configured to be at least partially blocked from the pumping chamber when the pumping chamber is in the open configuration. The degree to which the channel is blocked from the pumping chamber preferably varies with the change in relative position of the scroll members.

[0019] The channel can convey fluid from the inlet into the outermost pumping chamber of the scroll pump. For example, the channel can be provided on the base of the fixed scroll and adjacent to the outer peripheral wall of the fixed scroll. This wall can be a wall of the housing of the scroll pump. Alternatively, the channel can be provided on an outer flange of the base of the orbiting scroll.

[0020] The scroll pump can have several pumping chambers. For example, there can be one pumping chamber on each side of the involute wall of the orbiting scroll. Each of these two pumping chambers can be in the open configuration at the same time, such that each pumping chamber receives fluid along two respective flow paths, one pumping chamber conveying fluid from the inlet directly into the pumping chamber and the other pumping chamber conveying fluid from the inlet into the pumping chamber via the channel. When one of these two pumping chambers is in the closed configuration, the other of these two pumping chambers is preferably in the fully open configuration. In some embodiments, the channel can move across the intermediate involute wall as the relative orbiting motion between the scroll members.

[0021] The channel can be segmented along its length by a strip extending from one side to the other. This can provide support for a tip seal provided on the end of the involute wall facing the channel.

[0022] The scroll pump can have a plurality of said channels to increase the flow conductance of fluid to the respective pumping chambers.

[0023] The scroll pump can comprise a multi-open-end scroll pump comprising a plurality of inlets, the scroll pump comprising a plurality of said channels, each channel positioned adjacent to a respective inlet.

[0024] The scroll pump can be in the form of a scroll vacuum pump.

[0025] The orbiting scroll refers to a scroll that orbits during use of the scroll. It will be appreciated that the orbiting scroll itself is stationary when the pump is not in use. BRIEF DESCRIPTION OF DRAWINGS

[0026] Preferred features of the present application will now be further described with reference to the drawings, wherein: Figure 1 A top sectional view schematically illustrating 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 shows the inlet portion of the scroll pump of Figure 3 at different points in a wrap cycle of the pump. DETAILED DESCRIPTION

[0027] Figure 1 and 2 shows a schematic sectional view of an inlet portion of a conventional scroll pump 10. The scroll pump 10 includes two scroll members in the form of a fixed scroll 12 and an orbiting scroll 14, the orbiting scroll being driven by a motor (not shown) to orbit relative to the fixed scroll 12 about an orbiting axis that is offset from the center of the fixed scroll 12. The fixed scroll 12 includes a base 16 and an involute or spiral wall 18 that upstands from and is normal to the base 16. Similarly, the orbiting scroll 14 includes a base 20 and an involute or spiral wall 22 that upstands from and is normal to the base 20. The bases 16, 18 and involute walls 20, 22 of the scroll members, together with an outer peripheral wall 24 of the fixed scroll 12, define a plurality of pumping chambers therebetween, generally indicated at 26.

[0028] 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 chambers are in fluid communication with an inlet 28 of the scroll pump 10, or a closed configuration in which the pumping chambers are isolated from the inlet 28. The inlet 28 extends through the outer wall 24 of the fixed scroll 12. In the relative positions of the fixed scroll 12 and the orbiting scroll 14 as shown in Figure 1 , a first pumping chamber 30 and a second pumping chamber 32 are in the open configuration such that fluid can enter the first pumping chamber 30 from the inlet 28 along a first flow path, generally indicated at Fl, and fluid can enter the second pumping chamber 32 from the inlet 28 along a second flow path, generally indicated at F2. Each of the first and second flow paths Fl, F2 extends parallel to the bases 16, 18 of the scroll members.

[0029] When orbiting scroll 14 moves relative to stationary scroll 12 in an orbiting motion, each of first pumping chamber 30 and second pumping chamber 32 will in turn move to a closed configuration in which it is isolated from inlet 28. With further orbiting motion, the closed pumping chamber moves inward along a spiral path toward a central outlet (not shown) of scroll pump 10, becoming smaller in size to compress fluid trapped in the pumping chamber. Eventually, each pumping chamber is in fluid communication with the outlet to enable compressed fluid to be expelled from scroll pump 10.

[0030] When first pumping chamber 30 is in the open configuration, fluid enters first pumping chamber 30 through an open end of first pumping chamber 30 between involute wall 18 of stationary scroll 12 and involute wall 22 of orbiting scroll 14. When second pumping chamber 32 is in the open configuration, fluid enters second pumping chamber 32 through an open end of second pumping chamber 32 between outer wall 24 of stationary scroll 12 and involute wall 22 of orbiting scroll 14. The open ends of the pumping chambers tend to have a relatively small cross-sectional area. This can impose a restriction on the flow of fluid into the pumping chambers.

[0031] Figure 3 and 4 A schematic cross-sectional view of an inlet portion of an embodiment of scroll pump 10' is shown. Features of scroll pump 10' that are the same as features of scroll pump 10 have been indicated using the same reference numerals and will not be described again here. Scroll pump 10' differs from scroll pump 10 in that base 16 of stationary scroll 12 includes a channel 34 in the form of a cutout formed in base 16. Channel 34 is in fluid communication with inlet 28. Channel 34 is positioned adjacent to inlet 28 and extends lengthwise partially around an axis about which orbiting scroll 14 moves relative to stationary scroll 12.

[0032] As described in more detail below, channel 34 is positioned in stationary scroll 12 so that, in the open configuration, an additional flow path F3 can be established between inlet 28 and the pumping chambers. Referring to Figure 4 In the illustrated relative positions of stationary scroll 12 and orbiting scroll 14, additional flow channel F3 extends from inlet 28 to first pumping chamber 30 via channel 34. Fluid enters first pumping chamber 30 from channel 34 in a direction that is orthogonal to base 16, 20 of the scroll members and parallel to the longitudinal axis of scroll pump 10'. Thus, fluid enters first pumping chamber 30 from channel 34 (along additional flow path F3) in a direction that is orthogonal to the direction in which fluid enters first pumping chamber 30 directly from inlet 28 (along first flow path Fl). Positioning channel 34 adjacent to inlet 28 can minimize the length of additional flow path F3 and thus further improve the flow conductance of scroll pump 10'.

[0033] Figures 5 to 8 The first pumping chamber 30 is shown in a fully open configuration in which the radial distance between the end 36 of the involute wall 22 of the orbiting scroll 14 and the involute wall 18 of the fixed scroll 12 is greatest. In this position, the area of the outlet 38 of the channel 34 in fluid communication with the first pumping chamber 30 is also greatest. A first portion of fluid entering the scroll pump 10' from the inlet 28 enters the first pumping chamber 30 along the first flow path Fl, while a second portion of fluid entering the scroll pump 10' from the inlet 28 enters 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 is isolated from both the inlet 28 and the channel 34 by the involute wall 22 of the orbiting scroll 14.

[0034] In Figure 5 The position of the orbiting scroll 14 shown is 30 degrees of orbital movement from the position shown in FIG. 4. In this position, the first pumping chamber 30 is in an open configuration, while the second pumping chamber 32 is in a closed configuration. The first pumping chamber 30 remains in fluid communication with the inlet 28 via the first flow path Fl and the additional flow path F3, although both of these flow paths have been reduced in size in view of the movement of the orbiting scroll 14 relative to the fixed scroll. The second pumping chamber 32 is isolated from the inlet 28 by the involute wall 22 of the orbiting scroll 14.

[0035] Figure 6 The position of the orbiting scroll 14 relative to the fixed scroll 12 is shown after 90 degrees of orbital movement from the position shown in FIG. 4. The first pumping chamber 30 remains in an open configuration, but it has been substantially isolated from the channel 34 by the involute wall 22 of the orbiting scroll 14, such that fluid enters the first pumping chamber 30 substantially only via the first flow path Fl (although some fluid leakage from the channel 34 into the first pumping chamber 30 from underneath the involute wall 22 can be present). The second pumping chamber 32, on the other hand, 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 5 The position of the orbiting scroll 14 relative to the fixed scroll 12 is shown after 90 degrees of orbital movement from the position shown in FIG. 4. The first pumping chamber 30 remains in an open configuration, but it has been substantially isolated from the channel 34 by the involute wall 22 of the orbiting scroll 14, such that fluid enters the first pumping chamber 30 substantially only via the first flow path Fl (although some fluid leakage from the channel 34 into the first pumping chamber 30 from underneath the involute wall 22 can be present). The second pumping chamber 32, on the other hand, 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.

[0036] Figure 7 The position of the orbiting scroll 14 relative to the fixed scroll 12 is shown after 90 degrees of orbital movement from the position shown in FIG. 4. The first pumping chamber 30 remains in an open configuration, but it has been substantially isolated from the channel 34 by the involute wall 22 of the orbiting scroll 14, such that fluid enters the first pumping chamber 30 substantially only via the first flow path Fl (although some fluid leakage from the channel 34 into the first pumping chamber 30 from underneath the involute wall 22 can be present). The second pumping chamber 32, on the other hand, 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 6 The position of the orbiting scroll 14 relative to the fixed scroll 12 is shown after 90 degrees of orbital movement from the position shown in FIG. 4. The first pumping chamber 30 remains in an open configuration, but it has been substantially isolated from the channel 34 by the involute wall 22 of the orbiting scroll 14, such that fluid enters the first pumping chamber 30 substantially only via the first flow path Fl (although some fluid leakage from the channel 34 into the first pumping chamber 30 from underneath the involute wall 22 can be present). The second pumping chamber 32, on the other hand, 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.

[0037] Figure 8 The position of orbiting scroll 14 relative to fixed scroll 12 is shown after a 30 degree orbiting movement from the position shown. Figure 7 The position of orbiting scroll 14 relative to fixed scroll 12 is shown after a 30 degree orbiting movement from the position shown. First pumping chamber 30 is in a closed configuration in which it is completely isolated from inlet 28 by involute wall 22 of orbiting scroll 14. Second pumping chamber 32 remains in an open configuration but the amount of fluid entering the second pumping chamber via both second flow path F2 and additional flow path F3 is increased.

[0038] Thus, in this embodiment, after a 150 degree orbiting movement of orbiting scroll 14 relative to fixed scroll 12, first pumping chamber 30 has transitioned from a fully open configuration to a closed configuration.

[0039] Reference numerals 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 chamber 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

1. A scroll pump comprising: an inlet for receiving fluid to be pumped; an outlet for delivering pumped fluid from the scroll pump; and two scroll members comprising a fixed scroll and an orbiting scroll interleaved with the fixed scroll and mounted such that rotation of a motor imparts orbiting 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 delivering fluid from the inlet to the outlet and which, with orbiting motion 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 the base of one of the scroll members comprises a channel which is in fluid communication with the inlet and positioned such that, when the pumping chamber is in the open configuration, the pumping chamber receives fluid from the inlet along an additional flow path through the channel. The first fluid flow path is arranged to deliver fluid from the inlet and into a pumping chamber between the involute wall of the fixed scroll and one end of the involute wall of the orbiting scroll.

2. The scroll pump of claim 1, wherein, The first fluid flow path extends substantially parallel to the base of the scroll members.

3. The scroll pump of claim 1 or 2, wherein, The channel is positioned adjacent to the inlet.

4. The vortex pump of any of the preceding claims, wherein, The channel is elongate in shape and extends lengthwise around an axis of orbiting motion of the orbiting scroll relative to the fixed scroll.

5. The vortex pump of any of the preceding claims, wherein, 6. The scroll pump of claim 5, wherein the channel extends around the axis through an angle in the range 10 to 60 degrees, preferably in the range 15 to 30 degrees. The additional flow path is arranged to deliver fluid into the pumping chamber in a direction substantially orthogonal to the base of the scroll members.

7. The vortex pump of any of the preceding claims, 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.

8. The vortex pump of any of the preceding claims, wherein, The channel is shaped such that it is in fluid communication with the pumping chamber when the pumping chamber is in the open configuration and substantially isolated from the pumping chamber when the pumping chamber is in the closed configuration.

9. The vortex pump of any of the preceding claims, wherein, 10. The scroll pump of any preceding claim, comprising a plurality of pumping chambers and wherein the channel is arranged to deliver fluid from the inlet into an outermost pumping chamber. The channel is arranged to deliver fluid into two pumping chambers simultaneously, each of which is in the open configuration.

11. The vortex pump of any of the preceding claims, wherein, The channel is arranged to deliver fluid into only one of the two pumping chambers when the other pumping chamber is in the closed configuration.

12. The scroll pump of claim 11, wherein, The channel is located in the base of the fixed scroll.

13. The vortex pump of any of the preceding claims, wherein, The channel is located in the base of the orbiting scroll.

14. The vortex pump of any one of claims 1 to 12, wherein, 15. The scroll pump of 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. ​

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