Scroll pump
By integrating channel seals with varying involute wall heights and an intermediate outlet with a pressure relief valve, scroll pumps effectively mitigate gas leakage and power consumption, resulting in a compact, efficient design.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- EDWARDS LTD
- Filing Date
- 2025-11-26
- Publication Date
- 2026-06-11
Smart Images
Figure GB2025052589_11062026_PF_FP_ABST
Abstract
Description
[0001] M24B133 / JM - 1 -
[0002] SCROLL PUMP
[0003] FIELD OF THE INVENTION
[0004] The field of the invention relates to scroll pumps.
[0005] BACKGROUND
[0006] A scroll pump comprises two interleaving scrolls one of which has an orbital motion with respect to the other thereby trapping and pumping or compressing pockets of fluid between the scrolls. There is a potential gas leakage path between the end of the scroll walls of one scroll member and the base of the other scroll member, which leakage may raise ultimate pressure and increase power consumption. Seals such as, channel seals mounted on the base of the scroll member between adjacent wraps of the scroll, or tip seals mounted on the end of the scroll wall may be used to inhibit such leakage. Channel seals may provide particularly effective sealing.
[0007] SUMMARY
[0008] One aspect provides a scroll pump comprising: two scroll members comprising interleaving scrolls mounted such that rotation of a motor imparts an orbital motion to one scroll member with respect to the other scroll member, each of said two scroll members comprising a base wall from which involute walls forming said interleaving scrolls extend, said involute and base walls from respective scroll members defining a plurality of pumping channels for pumping fluid from a scroll inlet to a scroll outlet; wherein for each of said two scroll members, said base wall of said scroll member comprises a channel seal between adjacent wraps of said involute walls, such that an end surface of said involute wall of the other scroll member contacts and seals with said channel seal mounted on said base wall of said scroll member; said involute walls of said two scroll members having a portion with a first height towards said scroll inlet and a portion with a second shorter height towards said scroll outlet. M24B133 / JM - 2 -
[0009] Channel seals may provide a particularly effective seal between the involute wall of one scroll member and the base of the other scroll member. This effective seal allows embodiments to provide a change in height of the involute wall with a corresponding increase in compression to be supported without providing undue leakage. A decrease in the involute wall height_towards the exhaust, provides a decrease in swept volume with a corresponding power saving. In effect an increased volume ratio across the scroll is provided. Channel seals also allow the involute walls to be thinner than is the case with tip seals, leading to a more compact pump.
[0010] In some embodiments, said two scroll members comprise a fixed scroll member and an orbiting scroll member, an inner portion of said base wall of said orbiting scroll member from which said involute walls of said second shorter height extend being recessed within an outer portion of said base wall from which said involute walls of said first height extend; wherein bearings for mounting said orbiting scroll member on a shaft driven by said motor are mounted within said recessed inner portion of said orbiting scroll member.
[0011] Providing a change in height of the involute or scroll walls at a point along the length of the scroll means that one of the scrolls will have a recess in the centre portion of the base of the scroll. Although the recess could be in the fixed scroll member preferably it is in the orbiting scroll member. Providing the step due to the change in height of the involute or scroll walls in the base of the orbiting scroll provides a recess in the base of the orbiting scroll. This means the bearings mounting the orbital scroll can be located within the recess allowing them to be located towards the centre of gravity of the orbiting scroll member. This reduces couples and the corresponding uneven wear on the seals that arises due to these forces and in this way seal life is increased.
[0012] In some embodiments, a change in height of said involute walls is located at a point along said involute walls that is more than one wrap from said scroll inlet M24B133 / JM - 3 - and from said scroll outlet, preferably more than one and a half wraps, more preferably more than 2 wraps.
[0013] The change in height of the involute wall may be at or near, in some examples within a 1 / 2 wrap of the mid point of the scroll, when viewed with respect to number of wraps or turns. Providing the change in height of the involute walls towards the mid point of the scroll allows the reduction in power due to the reduction in swept volume towards the outlet to be significant, while still maintaining a suitable ultimate pressure. In this regard, extending the distance from the inlet improves the speed curve, while extending the distance from the outlet improves the power reduction. Locating the change in height away from both the inlet and the outlet allows for a significant power reduction and a satisfactory speed curve. It also means that the recess in the orbiting scroll member due to the change in height is of a diameter that the bearings fit within and is in a position that is towards the centre of gravity of the orbiting scroll member.
[0014] In some embodiments, said second shorter height is between 25 and 60% of said first height, preferably between 30 and 50%.
[0015] In some embodiments, said two scroll members comprise a fixed scroll member and an orbiting scroll member, said orbiting scroll member being mounted such that it is biased towards said fixed scroll member by a biasing means.
[0016] The fixed scroll and the orbiting scroll may be biased towards each other by mounting the orbiting scroll member for example in a spring-loaded fashion. Alternatively, the axial clearances between the two scroll members may be set to be very close perhaps by clamping the scroll members in position. The spring loading or small axial clearances are required for low gas leakage in the scroll pump and render channel seals particularly effective. M24B133 / JM - 4 -
[0017] In some embodiments, said scroll pump comprises an intermediate outlet between said scroll inlet and said scroll outlet.
[0018] In some embodiments, said two scroll members comprise a fixed scroll member and an orbiting scroll member and said intermediate outlet is in said base wall of said fixed scroll member between said portion of said involute wall having said first height and said portion of said involute wall having said second shorter height.
[0019] There may be some performance loss due to leakage that occurs at the change in height of the involutes and also at the site of an intermediate outlet, where one is provided. Arranging these two sources of potential leakage in substantially the same place mitigates their combined effect.
[0020] In some embodiments, said intermediate outlet is coupled to a pressure release valve.
[0021] An intermediate outlet coupled to a pressure relief valve may inhibit an excess build up of pressure within the scroll pump which the reduction in volume due to the change in height of the involute walls may cause. The pressure relief valve is configured to inhibit the pressure within the scroll pump rising above the pressure at the exhaust by an undue amount. Thus, where the pressure at the change in height of the involute walls, rises above atmospheric pressure by a certain amount the release valve will open and gas can be vented. This may occur where the pressure at the scroll pump inlet is high.
[0022] In some embodiments, said scroll pump comprises a bypass channel between said intermediate outlet and an exhaust channel from said scroll pump outlet said pressure relief valve being located on said bypass channel.
[0023] The bypass channel allows vented gas to be exhausted along with gas output at the scroll pump outlet. M24B133 / JM - 5 -
[0024] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of 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.
[0025] Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.
[0026] BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:
[0028] Figure 1 shows a cross section through a scroll pump according to one embodiment; and
[0029] Figure 2 shows a schematic plan view of a scroll pump according to an embodiment.
[0030] DESCRIPTION OF THE EMBODIMENTS
[0031] Before discussing the embodiments in any more detail, first an overview will be provided.
[0032] Scroll pumps with a pre-loaded channel seal are known to provide effective sealing. Embodiments, provide scroll pumps with channel seals that provide excellent axial sealing between the wall tips and the opposing scroll channels, leading to good ultimate pressure and low ultimate power. Embodiments additionally provide a step in the wall height of the scrolls, such that the wall heights are reduced at the outlet compared to the inlet. This change in height reduces exhaust capacity and compression power. The use of an intermediate outlet and a blow-off valve at the change in height can inhibit an excess build-up of pressure and improve performance still further, particularly during operation at high inlet pressure. M24B133 / JM - 6 -
[0033] Figure 1 shows a scroll pump 10 according to an embodiment. Scroll pump 10 comprises an orbiting scroll member 20 and a fixed scroll member 30. Orbiting scroll member 20 is mounted on a shaft 62 via a cam 52 such that rotation of motor 60 rotates shaft 62 and owing to the cam 52 provides an orbital motion of the orbiting scroll member 20 with respect to the fixed scroll member 30. During operation, scroll pump 10 pumps gas along pumping channels formed between the respective bases and interleaving involute walls of the scroll members from an inlet at the outer edge of the scroll towards an outlet towards the centre.
[0034] Orbiting scroll member 20 has a base from which involute walls 22 extend. Fixed scroll member 30 similarly has a base from which involute walls 32 extend. The scroll pump 10 comprises a step or change in the height of the involute walls towards the mid- point (in terms of number of wraps) of the scrolls. The change in height is such that the first outer portion of the involute walls 22a and 32a are longer than the second inner portion of the involute walls 22b and 32b, this reduces the cross-sectional area of the pumping channel towards the scroll pump outlet and further compresses the gas being pumped. This leads to a reduced swept volume downstream of the step which in turn leads to a lower power consumption. The shorter involute walls may be between 35% and 45% of the height of the longer involute walls. In this example they are 2.5 wraps from either end of the scroll.
[0035] In order to provide the change in height of involute walls in this embodiment there is a recess 25 in the base of the orbiting scroll, while the fixed scroll member 30 has a planar base. A bearing 40 for mounting the orbiting scroll member 20 on shaft 62 is located within this recess 25 and this provides a balanced orbiting scroll member and reduces couples that arise when the bearing is not towards the centre of gravity of the orbiting scroll member. This arrangement reduces the wear on the channel seals and provides for an improved design. M24B133 / JM - 7 -
[0036] In this embodiment, the orbiting scroll member is spring-mounted via spring 50 such that it is biased towards the fixed scroll. In other embodiments, it may be mounted with small clearances to provide the desired low leakage.
[0037] In this embodiment, there are channel seals 24, 34 within the pumping channels on the base of respective scroll members which seal with the involute walls 32, 22 of the corresponding scroll member. These channel seals provide an effective sealing mechanism between the ends of the involute walls and the base of the opposing scroll.
[0038] At the step change in height of the involute walls there is an increase in compression. There is also a gap in the involute wall of the fixed scroll member and this leads to an increase in leakage. The channel seals help mitigate this. In some cases there may be an intermediate outlet at this point (see Figure 2) that provides a flow path to a blow off valve, allowing excess pressure in the scroll pump to be vented.
[0039] Figure 2 shows a schematic plan view of the interleaving scrolls of the scroll pump of Figure 1 . Relative motion of fixed scroll member 30 and orbiting scroll member 20 pump fluid from scroll pump inlet 81 to scroll pump outlet 82. There is a change in height in the involute walls of the scrolls towards the mid-point of the scroll and there is a gap in the fixed scroll involute wall at this point. An intermediate outlet 70 is located in the base of the fixed scroll member at this point and this is connected to bypass channel 72 which comprises a blow off valve 74. This allows for any excessive increase in pressure which may for example, occur where there is a high inlet pressure, such as during pumpdown, to be relieved by the venting of gas through the intermediate outlet, bypass channel 72 and blow off valve 74. The vented gas then joins with the gas exhausted from scroll pump outlet 82 via exhaust line 84 which itself has a blow off valve 86 and the gasses are then output at exhaust 80. M24B133 / JM - 8 -
[0040] In summary embodiments provide a pump with: good axial sealing; low power consumption; low vibrations and a compact design. A bypass or blow-off valve may be used to reduce power at high inlet pressures (typically pressures above 500 mbar).
[0041] Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.
[0042] M24B133 / JM - 9 -
[0043] REFERENCE SIGNS
[0044] 10 scroll pump
[0045] 20 orbiting scroll member
[0046] 22, 22a involute wall
[0047] 22b reduced height involute walls
[0048] 24 channel seal
[0049] 25 recess in base of orbiting scroll
[0050] 30 fixed scroll member
[0051] 32, 32a involute walls
[0052] 32b reduced height involute walls
[0053] 34 channel seal
[0054] 40 bearings
[0055] 50 spring
[0056] 52 cam
[0057] 60 motor
[0058] 62 shaft
[0059] 70 intermediate outlet
[0060] 72 bypass channel
[0061] 74 blow off valve
[0062] 80 exhaust
[0063] 81 scroll pump inlet
[0064] 82 scroll pump outlet
[0065] 84 exhaust line
[0066] 86 exhaust blow off valve
Claims
M24B133 / JM - 10 -CLAIMS1 . A scroll pump comprising: two scroll members comprising interleaving scrolls mounted such that rotation of a motor imparts an orbital motion to one scroll member with respect to the other scroll member, each of said two scroll members comprising a base wall from which involute walls forming said interleaving scrolls extend, said involute and base walls from respective scroll members defining a plurality of pumping channels for pumping fluid from a scroll inlet to a scroll outlet; wherein for each of said two scroll members, said base wall of said scroll member comprises a channel seal between adjacent wraps of said involute walls, such that an end surface of said involute wall of the other scroll member contacts and seals with said channel seal mounted on said base wall of said scroll member; said involute walls of said two scroll members having a portion with a first height towards said scroll inlet and a portion with a second shorter height towards said scroll outlet.
2. A scroll pump according to claim 1 , wherein said two scroll members comprise a fixed scroll member and an orbiting scroll member, an inner portion of said base wall of said orbiting scroll member from which said involute walls of said second shorter height extend being recessed within an outer portion of said base wall from which said involute walls of said first height extend; wherein bearings for mounting said orbiting scroll on a shaft driven by said motor are mounted within said recessed inner portion of said orbiting scroll member.
3. A scroll pump according to any preceding claim, wherein a change in height of said involute walls is located at a point along said involute walls that is more than one wrap from said scroll inlet and said scroll outlet.
4. A scroll pump according to claim 3, wherein said change in height of said involute walls is located at a point along said involute walls that is more than oneM24B133 / JM - 11 - and a half wraps, more preferably more than 2 wraps from said scroll inlet and said scroll outlet.
5. A scroll pump according to any preceding claim, wherein said second shorter height is between 25 and 60% of said first height.
6. A scroll pump according to claim 5, wherein said second shorter height is between 30 and 50% of said first height.
7. A scroll pump according to any preceding claim, wherein said two scroll members comprise a fixed scroll member and an orbiting scroll member, said orbiting scroll member being mounted such that it is biased towards said fixed scroll member by a biasing means.
8. A scroll pump according to any preceding claim, wherein said scroll pump comprises an intermediate outlet between said scroll inlet and said scroll outlet.
9. A scroll pump according to claim 8, wherein said two scroll members comprise a fixed scroll member and an orbiting scroll member, said intermediate outlet being in said base wall of said fixed scroll member between said portion of said involute wall having said first height and said portion of said involute wall having said second shorter height.
10. A scroll pump according to claim 8 or 9, said intermediate outlet being coupled to a pressure relief valve.
11. A scroll pump according to claim 9 or 10, said scroll pump comprising a bypass channel between said intermediate outlet and an exhaust channel from said scroll pump outlet, said pressure relief valve being located on said bypass channel.