TW201740022A - Scroll pump tip sealing - Google Patents

Abstract

A scroll pump (10) has a fixed scroll (26) and an orbiting scroll (28). The base members (38, 46) of the scrolls are provided with respective base seals (54, 56) to seal between the major surfaces (36, 44) of the base members (38, 46) and the opposed scroll wall tip faces (40, 48). One or more orbiting scroll biasers are provided to resiliently push the fixed and orbiting scrolls (26, 28) together.

Description

Scroll pump end seal

The present invention relates to a scroll pump end seal.

A scroll compressor or pump is known to include a fixed scroll, an orbiting scroll, and a drive mechanism for the orbiting scroll. The drive mechanism is configured to cause the orbiting scroll to be wound relative to the fixed vortex to cause a fluid to be pumped between a pump inlet and a pump outlet. The fixed scroll and the orbiting scroll each comprise an upstanding scroll wall extending from a generally circular base plate. Each scroll wall has an end face or end face that is disposed away from the respective bottom plate and extends generally perpendicular to the respective bottom plate. The orbiting scroll wall is configured to engage the fixed scroll wall during the orbiting of the orbiting scroll such that the relative orbital motion of the scroll causes the continuous volume of gas to be enclosed between the walls of the scroll and The inlet is pumped into the air bag at the outlet. A scroll pump can be a dry pump and is not lubricated. In this case, to prevent back leakage, the end of each scroll wall is provided with an end seal for sealing against the bottom of the other scroll. The end seal is positioned in a channel defined in the end of the scroll wall and is typically made of PTFE. There may be a small gap between the pedestal of each channel and the opposing face of the end seal such that the fluid occupying the gap in use creates a uniform force that forces the end seal toward and against the bottom of the other vortex . The end seal closes the gap between the scrolls due to manufacturing and operational tolerances and reduces the leakage to an acceptable level. Typically, the one end seal is narrower than its passage such that there is a radial clearance between the end seal and the opposing side wall of the passage. During the relative orbiting motion of the scroll, the end seal is urged against one of the side walls for its portion of motion and against the other side wall for another portion of its motion. As the end seal moves back and forth between these positions, the leakage increases due to the presence of a leak path through one side formed from the seal to the other side of the seal. End seals are known to typically have an aspect ratio of height to radial width 1:1. That is, the radial extent of the end seal is equal to the height of the end seal such that the end seal has a square cross section. Thus, the end seals are relatively rigid in the radial (or lateral) direction. This relative stiffness slows the movement of the end seals as the end seals move radially between the sidewalls of the end seal passages, thereby increasing leakage. There are applications such as portable mass spectrometers that require a small dry pump capable of one of about 0.1 m ² /hr to 3.0 m ² /hr. This need is currently met by a diaphragm pump. However, the diaphragm pump still has a relatively large pumping capacity and has a poor ultimate pressure due to its internal valve. One of the typical limit pressures of this pump is 2 mbar. Scroll pumps provide better performance. However, reducing the size of a scroll pump presents the problem of actuating the end seal. If the scroll wall is made thin for the purpose of reducing the radial dimension of the pump, the end seal must be made to be correspondingly thin. For example, if the scroll wall is thinned to a thickness of 1.0 mm, the end seal will have a thickness of about 0.5 mm. At this thickness, there will be minimal actuation force under the end seal to urge the end seal against the opposing scroll.

The present invention provides a scroll pump as defined in claim 1.

Referring to Figure 1, a scroll pump 10 includes a pump housing 12 and a scroll drive. In this example, the scroll drive includes a drive shaft member 14 having a longitudinal shaft 16 and has a mounting parallel to the longitudinal direction. The shaft 16 is offset from the longitudinal axis 16 by one of the eccentric members 18 of one of the shafts 20. The eccentric member 18 can be secured to one of the separate bodies of the drive shaft member 14. The scroll drives 14, 18 are driven by a motor including a stator 22 and one of the rotors 24 coupled to the drive shaft member 14. The scroll pump 10 has a scroll group including a fixed scroll 26 and an orbiting scroll 28. The scroll sets 26, 28 are operable to pump fluid along a fluid flow path between a pump inlet 30 and a pump outlet 32. The fixed scroll 26 includes a spiral or inner swirl wall 34. The scroll wall 34 extends perpendicularly from one major surface 36 of the generally circular base member 38 and has an end face or end face 40 spaced from the major surface 36. The end face 40 can be disposed generally parallel to the major surface 36 and defines one of the free ends of the fixed scroll wall 34. The base member 38 can be a portion of the pump housing 12 (as illustrated by Figure 1) or a separate component disposed within the pump housing. The orbiting scroll 28 includes a spiral or inner swirling wall 42. The scroll wall 42 freely extends from one of the major sides of one of the major circular base members 46. The scroll wall 42 has an end face or end face 48 spaced from the major surface 44 and defines one of the free ends of the orbiting scroll wall 42. End face 48 can be generally disposed parallel to major surface 44. The fixed scroll 26 and the orbiting scroll 28 are nested such that the orbiting scroll wall 42 cooperates or engages with the fixed scroll wall 34 during the orbital movement of the orbiting scroll 28. The relative orbital movement of the scrolls 26, 28 causes a continuous volume of gas to be captured in the bladder defined between the scrolls and pumped from the inlet 30 to the outlet 32. Referring additionally to Figure 2, the scroll pump 10 can be a dry pump in which the scrolls 26, 28 are not lubricated. To prevent or at least reduce back leakage through the respective gaps 50, 52 between the end faces 40, 48 of the scroll walls 34, 42 and the opposing major surfaces 36, 44 of the base members 38, 46, Base seals 54, 56 are used to close the gaps 50, 52. Still referring to FIG. 2, a base seal 54 is disposed on the major surface 36 of the base member 38 between adjacent turns of the fixed scroll wall 34. In the illustrated example, the base seal 54 at least substantially covers the major surface 36 between the adjacent turns of the fixed scroll wall 34. Similarly, a base seal 56 is provided on the major surface 44 of the base member 46 between the adjacent turns of the orbiting scroll wall 42. In the illustrated example, the base seal 56 at least substantially covers the major surface 44 between the adjacent turns of the orbiting scroll wall 42. Although not necessary, at least one of the base seals 54, 56 can have a sealing biasing member 58, 60 disposed between the base seal and the respective major surfaces 36, 44. The seal biasing members 58, 60 or each of the seal biasing members 58, 60 are configured to bias the respective base seals 54, 56 away from the respective major surfaces 36, 44. The seal biasing members 58, 60 or each of the seal biasing members 58, 60 can assist in pressing the respective base seals 54, 56 against the opposing end faces 40, 48. Referring to FIG. 3, the scroll pump 10 is provided with bearing systems 66, 68 for supporting the drive shaft member 14. The bearing system can include two bearing units 66, 68 disposed at axially spaced locations along the drive shaft member 14. The bearing units 66, 68 can each include one or more rolling bearings. In the illustrated example, each bearing unit 66, 68 includes a single rolling bearing. The rolling bearing 66 is disposed at the end 14(1) of the drive shaft member 14 that is located furthest from the orbiting scroll 28 and the rolling bearing 68 is disposed adjacent the eccentric member 18. The end 14(1) of the drive shaft member has a reduced diameter portion for defining an abutment face 70 disposed perpendicular to the longitudinal axis 16. The bearing unit 66 is seated on the reduced diameter portion 14(1) against the abutment surface 70. The bearing unit 66 is pressed against the abutment surface 70 by an orbiting scroll biasing member 72. The orbiting scroll biasing member can include one or more resilient bodies. The orbiting scroll biasing member 72 can, for example, include one or a plurality of resilient members such as a C-shaped or Belleville washer. The orbiting wrap biasing member 72 can be held against the bearing unit 66 by a cap 74 that is secured to the pump housing 12. In other examples, the orbiting wrap biasing member 72 can be held in place by clamping the plate to one of the pump housings 12 (or integral with the pump housing 12). The drive shaft member 14 is adjacent the eccentric member 18 having a second reduced diameter portion for defining an abutment surface 76. The bearing unit 68 is seated on a second reduced diameter portion that engages both the abutment surface 76 and one of the end faces of the eccentric member 18 such that one of the orbiting scroll bias members 72 will be provided via the bearing units 66, 68 and the drive shaft member 14. The axial thrust is transmitted to the eccentric component. Optionally, a second orbiting scroll biasing member 78 can be provided to act directly on the bearing unit 68. The second orbiting scroll biasing member 78 can be pressed against the bearing unit 68 by an annular member 80 that is fixed to the pump housing 12 or one of the integral portions of the pump housing 12. The second orbiting scroll biasing member 78 can include one or more resilient bodies. The second orbiting scroll biasing member 78 can, for example, comprise one or more resilient members such as a C-shaped or Bell-shaped gasket. Still referring to FIG. 3, the orbiting scroll 28 is provided with a bearing housing 82 and a bearing 84 housed in the bearing housing. The bearing housing 82 protrudes from a second side 86 of one of the orbiting scroll base members 46 disposed opposite the first side (this first side defines the major surface 44). The bearing housing 82 can be integrally formed with the base member 46 as an annular member or as one of the base members. The bearing 84 has an axial centerline or axis of rotation that is at least substantially in line with the axis 20 of the eccentric member 18. The orbiting scroll 28 is coupled to the scroll drives 14, 18 by the eccentric member 18 engaging the bearing 84. The bearing 84 is a single rolling bearing and is seated between the eccentric member 18 and the base member 46 such that the orbiting scroll biasing member 72 (and the orbiting scroll biasing member 78, in the case of setting) will be passed via the bearing 84. The axial thrust provided is transmitted from the eccentric member 18 to the orbiting scroll 28. The axial thrust provided by the orbiting scroll biasing members 72, 78 or each of the orbiting scroll biasing members 72, 78 is configured to resiliently urge the fixed scroll 26 and the orbiting scroll 28 together. The orbiting scroll 28 is provided with at least one balancing mass 88 that is configured such that the orbiting scroll has a center of mass disposed in a plane 90 extending through the bearing 84 transverse to the axial centerline of the bearing. In the illustrated example, the plane 90 is disposed at least substantially perpendicular to the centerline of the bearing 84. In the illustrated example, the plane 90 also extends through the bearing housing 82 that is at least substantially parallel to the base member 46. The balance mass 88 or each balance mass 88 may be spaced apart from or associated with the second side 86 (or bearing housing 82) of the orbiting scroll base member 46 by a coupling structure 94 (or bearing housing) The connection has a relatively low (or negligible) effect on the position of the center of mass of the orbiting scroll 28. Connection structure 94 can, for example, include one or more relatively narrow rods or the like. The bearing housing 82 has a first end free end 92 spaced from the second side 86 of the orbiting scroll base member 46 and the balancing mass 88 or each balancing mass 88 has a spacing from the second side 86 that is greater than One of the distances of at least one of the second distances. The bearing 84 has a first side facing the second side 86 (and the fixed scroll 26) of the base member 46 and a second side facing away from the base member 46 (and the fixed scroll 26). The second side of the bearing 84 is spaced apart from the second side 86 of the base member 46 and the fixed scroll 26 by a respective first distance and the mass body 88 or each mass body 88 has a second side 86 and a fixed scroll 26 At least one end of each of the second distances greater than the respective first distances is spaced apart. 4 is a plan view of one of the fixed scrolls 26 with the base seal 56 omitted. The fixed scroll wall 34 can extend from the periphery of the base member 38 to its center and has an inner end disposed adjacent one of the ports 98 that is in fluid connection with the pump outlet 32. However, in some examples, the fixed scroll wall 34 may not extend to the center of the base member 38 and may alternatively have its inner end positioned a radial distance R1 away from the center, the radial distance R1 being between the scroll walls The radial distance R2 of the outer end is between about 0.25 and 0.5 times. Although not necessary, the origin or the origin of the radii R1, R2 may coincide with the center of the base member 38 or port 98. Although not shown in the drawings, the orbiting scroll wall 42 can similarly be proportioned to the fixed scroll wall such that both of the scroll walls 34, 42 are disposed substantially at their respective centers from the base members 38, 46. The inner end and the outer end at the same radial distance R1, R2. By increasing the radial distance R1 to about 0.25 times to 0.5 times R2, the peak pressure generated between the scrolls 26, 28 during roughing of the pump can be reduced. The force exerted by the one or more orbiting scroll biasing members is sufficient to overcome the pressure load that would be generated when the scroll pump was used would tend to separate the fixed scroll and the orbiting scroll. The force provided by the or the orbiting scroll biasing members should be sufficient to balance the pressure load and result in sufficient engagement between the base seal and the opposing end faces to provide a reliable seal. In particular, the or the orbiting scroll biasing member should be configured to overcome the peak pressure to ensure that the end faces 40, 48 remain in contact with the respective base seals 54, 56. If the biasing force must be relatively high to overcome the force generated by the relatively high pressure during roughing, then when the scroll pump is operated at the limit and the force generated by the pressure is relatively low, there is a need to be absorbed by the base seal. A relatively large over-biasing force. Since a typical scroll pump can operate up to about 90% of its operational life, absorbing a relatively large over-biasing force can cause excessive wear on the base seal. If the radial distance R1 is about 0.5 times the radial distance R2, then the scroll pump must be operated when the roughing pump is operated under roughing pressure and by appropriate selection of the orbiting scroll biasing member. The force generated by the pressure that overcomes the orbiting scroll biasing member can be significantly reduced, and the excessive biasing force applied to the base seal when the scroll pump is operated in extreme limits can be correspondingly reduced. If the radial distance R1 is about 0.25 times the radial distance R2, the force generated by the pressure can remain at least substantially constant at all inlet pressures. This allows the orbiting scroll bias to be selected to provide a biasing force that is only a small amount greater than the force generated by the pressure that would be present under all operating conditions. Thus, the force absorbed by the base seals 54, 56 can be relatively small and constant, thereby minimizing wear on the seal. FIG. 5 shows features of another scroll pump 110. Many of the features or parts of the scroll pump 110 correspond to or resemble the features of the scroll pump 10. The same reference numerals are used in FIG. 5 as those in FIGS. 1 through 3 to indicate such features or parts and may not be further described in order to avoid redundancy. The scroll pump 110 differs from the scroll pump 10 in that the drive shaft member 14 passes through the fixed scroll 26 to place the motors 22, 24 on the exhaust side of the pump. As with the example shown in Figures 1-3, although the fixed scroll base member 38 is shown as part of the pump housing 12, it can be disposed in a separate portion of the pump housing. In this example, the bearing system supporting the drive shaft member 14 includes two bearing units 66, 68 that are disposed at spaced apart locations along the length of the drive shaft member. The bearing unit 68, which is disposed closest to the eccentric member 18, is seated in or on the fixed scroll base member 38. In this example, there is only one orbiting scroll biasing member 72 and this orbiting scroll biasing member 72 is disposed between the base member 38 and the bearing unit 68. Although not shown, one of the second orbiting scroll bias members acting on the bearing unit 66 can be provided. In this case, the second orbiting scroll biasing member will act on the scroll side of the bearing unit 68 in a similar manner as the orbiting scroll biasing member 72. The orbiting scroll biasing member or each orbiting scroll biasing member causes the orbiting scroll 28 to be pulled toward the fixed scroll 26. The orbiting scroll biasing member or each orbiting scroll biasing member can include one or more resilient bodies. The orbiting scroll bias or each orbiting scroll bias may comprise, for example, one or a plurality of resilient members of a C-shaped or shell-shaped washer. In the example illustrated by FIG. 5, the bearing 84 between the eccentric member 18 and the orbiting scroll 28 is received in and surrounded by an aperture (or housing) 82 defined by the orbiting scroll base member 46. The orbiting scroll 28 is configured such that the center of mass of the orbiting scroll is at least one or more of the balance masses 88 in the plane of the base member 46 that passes through the bearing 84 and is perpendicular to the axial centerline of the bearing. The or the balance mass 88 can be integral with or directly secured to the second side 86 of the base member 46 to the second side 86 of the base member 46. A balancing mass 88 can be, for example, disposed on one of the annular projections on the base member 46. In other examples, the balance mass or each balance mass may be supported on a connection structure in a manner similar to the balance quality shown in Figures 1-3. The base seal provides a relatively large area for absorbing a force applied by the opposing end faces as compared to conventional end seals and thus correspondingly reduces the wear rate of the base seal. In addition, the wear should be reduced because the end faces of the wrap wall only contact any portion of the surface area of the respective pedestal seal that gives the orbital position. For the same reason, the peak temperature due to friction heating of the susceptor seal can be reduced. Also, due to the occurrence of wear, the scrolls will simply move closer together under the influence of the orbiting scroll biasing members. This is especially advantageous if the pump is operated at high speeds where the wear rate is generally high. When a scroll pump such as one of the pumps 10, 110 is initially assembled, a slight difference in the height of the scroll wall can result in a small leak across the base seal. This can be reduced at least by providing a seal bias between at least one scroll and a respective base seal such as the seal biasing members 58, 60 shown in FIG. While not limited to such materials, the base seal can be made of polytetrafluoroethylene (PTFE) and, if provided, the seal bias can comprise a relatively thin layer of expanded PTFE or another suitable plastic foam. Advantageously, a PTFE base seal has self-lubricating properties to facilitate sliding of the end face of the scroll wall above the base seal. In some examples, the base seal material 1 can be loaded with a dry lubricant, such as graphite, to promote sliding of the end faces over the base seal. The pedestal seal can be a generally flat body and can be produced from a sheet of material by, for example, laser cutting or stamping. The base seal can have a generally circular outer perimeter. The base seal may be provided with a spiral groove for receiving a wrap of the wrap. The helical groove can have a width that at least substantially corresponds to the width of the wrap wall where it meets the base member. The base seal can be secured to the scroll by an adhesive or a mechanical fastener such as a screw. Although not limited to this example, the scroll may be a hard anodized aluminum scroll. A precision machining of the end faces of the scroll walls (for example, by polishing) can be utilized to facilitate sliding over a susceptor seal. The end of the scroll wall may also be chamfered or rounded to promote slippage. Conventionally, a scroll pump has a plurality of bearings between the scroll drive and the orbiting scroll. This is to provide rigidity and to prevent metal-to-metal contact between the orbiting scroll and the fixed scroll. In the illustrated example, there is only one bearing between the scroll drive and the orbiting scroll. This provides compliance to allow the orbiting scroll to preferably abut against the fixed scroll mount, wherein at least substantially no sloshing action is caused by the drive shaft member, the eccentric member, and the orbiting scroll about the alignment of the fixed scroll. . Providing an orbiting wrap having one or more balancing masses to place the center of mass of the orbiting wrap in the plane of a single bearing between the wrap drive and the orbiting wrap to at least substantially prevent orbiting wraps The tilt can occur if the scroll drive acts on the orbiting scroll behind the center of mass. The orbiting scroll biasing member described in connection with the illustrated example should not be considered limiting. In principle, the or the orbiting scroll biasing member can comprise any suitable one or more resilient bodies capable of providing a desired biasing force. In other examples, an orbiting scroll biasing member can include a plurality of compression springs disposed at spaced apart intervals around the periphery of the scroll drives 14, 18. The compression spring can be captured or positioned between one or more suitable flat members, such as a gasket that can be provided with a projection to assist in positioning one end of a compression spring. It will be understood that although the orbiting scroll bias shown in the drawings acts directly on the bearing unit, in other examples the spacer or washer can be inserted between a biasing member and a bearing unit and will It is understood that such spacers or gaskets can be provided with a structure to assist in positioning the biasing members. Although not limited to these specifications, the provision of a pedestal seal with orbital scroll bias allows for the production of an operating capacity of 0.1 m ³ /hr to 0.4 m ³ /hr and a limit pressure of 0.1 mbar. Scroll pump. The pump can operate from 3000 rpm to 5000 rpm and has a scroll wall having a thickness of less than 1.0 mm. The thickness of the scroll wall can be in the range of 0.5 mm to 1.0 mm or 0.7 mm to 1.0 mm.

10‧‧‧ Scroll pump/pump
12‧‧‧ pump housing
14‧‧‧Drive shaft/scroll drive
14(1) ‧‧‧End/Reduced Diameter Section
16‧‧‧ longitudinal axis
18‧‧‧Eccentric parts / scroll drive
20‧‧‧Axis
22‧‧‧stator/motor
24‧‧‧Rotor/Motor
26‧‧‧ Fixed Scroll/Vortex
28‧‧‧ orbiting scroll/vortex
30‧‧‧Pump entrance/entry
32‧‧‧ pump outlet/export
34‧‧‧Spiral/inner vortex wall/vortex wall/fixed scroll wall
36‧‧‧Main surface
38‧‧‧Base parts
40‧‧‧End/end face/vortex wall end face
42‧‧‧Spiral or internal vortex wall/vortex wall/orbiting scroll wall
44‧‧‧Main surface
46‧‧‧Base parts/orbiting scroll base parts
48‧‧‧End/end face/vortex wall end face
50‧‧‧ gap
52‧‧‧ gap
54‧‧‧Base seals
56‧‧‧Base seals
58‧‧‧Sealing bias
60‧‧‧Sealing bias
66‧‧‧Bearing system/bearing unit/rolling bearing
68‧‧‧Bearing system/bearing unit/rolling bearing
70‧‧‧Adjacency
72‧‧‧ orbiting scroll biasing member
74‧‧‧Cap
76‧‧‧Adjacent faces
78‧‧‧Second orbiting scroll biasing member/optional orbiting scroll biasing member/orbiting scroll biasing member
80‧‧‧ ring parts
82‧‧‧ Bearing housing / orifice / housing
84‧‧‧ bearing
86‧‧‧ second side
88‧‧‧Balance quality/quality subject
90‧‧‧ plane
92‧‧‧Free end
94‧‧‧ Connection structure
98‧‧‧port
110‧‧‧ Scroll pump/pump
R1‧‧‧radial distance/radius/first radial distance
R2‧‧‧ Radial distance/radius

In the following disclosure, which is given by way of example only, reference is made to the drawings in which: FIG. 1 is a schematic diagram of a scroll pump; FIG. 2 is a schematic diagram of a scroll pump sealing system. 1 is an enlarged view of a portion of FIG. 1; FIG. 3 is another portion of FIG. 1 illustrating the features of a scroll drive and a scroll pump bearing system; FIG. 4 is a fixed scroll of a scroll pump A schematic plan view; and Figure 5 is a schematic illustration of one of Figure 3 generally showing an alternative scroll pump configuration.

10‧‧‧ Scroll pump/pump

12‧‧‧ pump housing

14‧‧‧Drive shaft/scroll drive

16‧‧‧ longitudinal axis

18‧‧‧Eccentric parts / scroll drive

20‧‧‧Axis

22‧‧‧stator/motor

24‧‧‧Rotor/Motor

26‧‧‧ Fixed Scroll/Vortex

28‧‧‧ orbiting scroll/vortex

30‧‧‧Pump entrance/entry

32‧‧‧ pump outlet/export

34‧‧‧Spiral/inner vortex wall/vortex wall/fixed scroll wall

36‧‧‧Main surface

38‧‧‧Base parts

40‧‧‧End/end face/vortex wall end face

42‧‧‧Spiral/inner vortex wall/vortex wall/orbiting scroll wall

44‧‧‧Main surface

46‧‧‧Base parts/orbiting scroll base parts

48‧‧‧End/end face/vortex wall end face

54‧‧‧Base seals

56‧‧‧Base seals

66‧‧‧Bearing system/bearing unit/rolling bearing

68‧‧‧Bearing system/bearing unit/rolling bearing

72‧‧‧ orbiting scroll biasing member

82‧‧‧ Bearing housing / orifice / housing

84‧‧‧ bearing

86‧‧‧ second side

88‧‧‧Balance quality/quality subject

Claims (13)

A scroll pump comprising: an orbiting scroll; a fixed scroll; a scroll drive configured to impart an orbiting motion to the orbiting scroll relative to the fixed scroll; At least one orbiting scroll biasing member acting on the scroll drive to urge the fixed scroll with the orbiting scroll; wherein the orbiting scroll includes a first major surface An orbiting scroll base member, an orbiting scroll wall extending from the first major surface toward the fixed scroll, and the fixed scroll includes a fixed scroll base member having a second major surface, a fixed scroll wall extending from the second major surface toward the orbiting scroll, the orbiting scroll wall having an orbiting scroll end face facing the second major surface, and the fixed scroll wall having the facing One of the first major surfaces is a fixed scroll end face, and the orbiting scroll base member has a first base seal disposed between adjacent turns of the orbiting scroll wall, the first base a seal slidably engaging the fixed scroll end face to the first major surface and the fixed scroll end Sealing between the faces, and the fixed scroll base member has a second base seal disposed between the adjacent turns of the fixed scroll wall, the second base seal being surrounded by the vortex The end face of the roll is slidably engaged to seal between the second major surface and the end face of the orbiting scroll. The scroll pump of claim 1, wherein the first base seal and the second base seal cover the respective major surfaces between the adjacent turns of the respective scroll walls. The scroll pump of claim 1, wherein at least one of the first base seal and the second base seal is disposed between the base seal and the respective major surfaces to enable the The base seal is biased away from the seal biasing member of one of the respective major surfaces. A scroll pump according to claim 1, wherein the scroll drive includes a drive shaft member and an eccentric member, and the scroll pump further includes a bearing for supporting the drive shaft member at axially spaced apart positions system. A scroll pump according to claim 4, wherein the bearing system includes at least two bearing units supporting the drive shaft member, wherein the at least one orbiting scroll biasing member acts on at least one of the bearing units. The scroll pump of claim 4, wherein the at least two bearing units comprise a first bearing unit and one of the second bearing units axially spaced relative to the first bearing unit, the bearing units each including at least one Rolling bearings. A scroll pump according to claim 1, wherein the orbiting scroll is coupled to the scroll drive via a bearing carried by the orbiting scroll and has at least one balance mass, the at least one balance mass configuration The center of mass of the orbiting scroll is located in a plane extending through the bearing and transverse to an axial centerline of the bearing. A scroll pump according to claim 7, wherein the bearing in the bearing housing is a single rolling bearing. The scroll pump of claim 7, wherein the orbiting scroll has a first side defining one of the first major surfaces and is disposed opposite the first side and spaced apart from the first side Two sides, and the at least one balance mass is coupled to the second side such that the second side is disposed between the first side and the at least one balance mass. A scroll pump according to claim 9, wherein the orbiting wrap includes a bearing housing in which the bearing is housed, the bearing housing projects from the second side, and the at least one balance mass is configured such that the plane is parallel to The orbiting wrap base member extends through the bearing housing. A scroll pump according to claim 10, wherein the bearing housing has a first distance spaced from the second side of the orbiting scroll base member, and the at least one balance mass has been disposed The orbiting scroll base member is at least one end greater than a second distance of the first distance. A scroll pump according to claim 1, wherein the bearing has a first side facing the fixed scroll base member and is spaced apart from the fixed scroll base member and spaced apart from the fixed scroll base member One of the second sides of the distance, and the at least one mass body has at least one end spaced apart from the fixed scroll base member by a second distance greater than the first distance. The scroll pump of claim 1, wherein at least one of the fixed scroll wall and the orbiting scroll wall has: an inner end disposed on and defined on the respective base member An origin is at a first radial distance R1; and an outer end is disposed at a second radial distance R2 from the origin, and the R1 is between 0.25 times R2 and 0.5 times R2 between.