Adjustable vortex pump

Abstract

The present invention provides a vortex pump, which includes a movable scroll and a fixed scroll, wherein when the movable scroll revolves around its orbital axis, the orbital axis of the movable scroll can move in a radial direction relative to the fixed scroll, or wherein when the movable scroll revolves around its orbital axis, the fixed scroll can move in a radial direction relative to the movable scroll.

Description

Technical Field

[0001] The invention relates to a vortex pump, in particular to a vacuum vortex pump. Background Art

[0002] A known scroll compressor or pump comprises a fixed scroll, a movable scroll and a drive mechanism for the movable scroll. The drive mechanism is configured to cause the movable scroll to orbit relative to the fixed scroll to cause fluid to be pumped between a pump inlet and a pump outlet. The fixed scroll and the movable scroll each include an upright vortex wall extending from a generally circular base plate. Each vortex wall has an end face or a top face that is disposed away from the corresponding base plate and extends generally perpendicular to the corresponding base plate. The movable vortex wall is configured to engage with the fixed vortex wall during the orbit of the movable scroll, so that the relative orbital motion of the vortex causes a continuous volume of gas to be enclosed in a recess defined between the vortex walls and pumped from the inlet to the outlet.

[0003] In order to expand their use, there is a continuing need for miniaturization of scroll pumps. However, the inventors have found that as the capacity of scroll pumps decreases, internal leakage becomes an increasingly serious problem. Such leakage has a negative impact on the ultimate pressure that the pump can achieve. In fact, below a certain pump capacity, it may not be possible to have a minimum clearance between the scroll members that will not get stuck and also to have an average or maximum radial clearance that provides acceptable performance.

[0004] The present invention solves, at least to some extent, these and other problems of known scroll pumps. Summary of the invention

[0005] Therefore, in a first aspect, the present invention provides a vortex pump comprising a movable scroll and a fixed scroll. The movable scroll has an orbital axis. When the movable scroll rotates around its orbital axis, the orbital axis of the movable scroll can move in a radial direction relative to the fixed scroll. In addition, or alternatively, when the movable scroll orbits around its orbital axis, the fixed scroll can move in a radial direction relative to the movable scroll. Preferably, when the movable scroll orbits around its orbital axis, the movable scroll moves relative to the fixed scroll by pivoting or translating the drive shaft.

[0006] This adjustable scroll pump enables the orbiting scroll to be placed in its optimal radial position. This allows the radial clearance between the scrolls to be nearly constant in all crank orientations. The optimized positioning of the orbiting scroll allows the use of a smaller radial clearance, which leads to improved performance including ultimate pressure and power.

[0007] Preferably, the scroll pump further comprises a first bearing coupled to a drive shaft for driving the movable scroll member. Preferably, the first bearing is movable together with the drive shaft in a direction substantially perpendicular to the rotation axis of the drive shaft.

[0008] Typically, the first bearing is coupled to a housing element of the vortex pump, the housing element being movable relative to the fixed scroll member when the drive shaft rotates. Preferably, the housing element is movable in a plane transverse to the axis of rotation of the vortex pump drive shaft. Preferably, the movable housing element can have its position fixed relative to the fixed scroll member. The position in which the housing element is fixed can be selected by the user.

[0009] Additionally or alternatively, the scroll pump comprises a second bearing coupled to the drive shaft and to a bearing bracket that is flexible in the axial direction.Preferably, in use, the flexible bearing bracket substantially eliminates movement of the rotor shaft in a radial direction.

[0010] Typically, the first bearing is coupled to the drive shaft such that the fixed scroll is positioned between the first bearing and the orbiting scroll. Typically, the first bearing is located at or substantially at an end of the drive shaft.

[0011] In another aspect, the present invention provides a method for storing a device having a capacity of less than 5 m 3 / h of a vortex chamber of a vortex pump, the vortex chamber includes a movable vortex member and a fixed vortex member, the movable vortex member and the fixed vortex member each include an axially extending vortex wall, wherein when the movable vortex member revolves, the minimum radial gap between the axially extending vortex wall of the movable vortex member and the axially extending vortex wall of the fixed vortex member is less than about 0.060 mm.

[0012] Such a clearance cannot be achieved with known scroll pumps of said capacity.

[0013] In yet another aspect, the present invention provides a movable scroll member and a fixed scroll member of a vortex pump, wherein the movable scroll member has an orbital axis and the fixed scroll member has a longitudinal axis, wherein the orbital axis and the longitudinal axis are coaxially aligned with a deviation of less than about ±0.030 mm, preferably less than about ±0.010 mm.

[0014] In yet another aspect of the present invention, a method for centering an orbiting scroll and a non-orbiting scroll of a vortex pump is provided, the vortex pump including an orbiting scroll and a non-orbiting scroll maintained radially separated during pumping, the orbiting scroll being coupled to a drive shaft via an eccentric member, the drive shaft having an axis of rotation.

[0015] The method comprises, in a first step, rotating the eccentric member about the rotation axis of the drive shaft to exert an orbiting motion on the movable scroll. Then, while the movable scroll is orbiting, the orbiting axis of the movable scroll or the longitudinal axis of the fixed scroll is moved relative to the other in a first direction substantially perpendicular to the rotation axis of the drive shaft until the movable scroll engages the fixed scroll. At the time of the engagement, the one of the orbiting axis of the movable scroll or the longitudinal axis of the fixed scroll that has moved is in a first engagement position.

[0016] The method further comprises the step of causing the orbital axis of the orbiting scroll or the longitudinal axis of the fixed scroll, whichever has moved, to move relative to the other in a second direction substantially opposite to the first direction until the orbiting scroll reengages the fixed scroll. During the engagement, the orbital axis of the orbiting scroll or the longitudinal axis of the fixed scroll, whichever has moved, is in a second engagement position.

[0017] The method also includes positioning the orbital axis of the movable scroll member or the longitudinal axis of the fixed scroll member that has moved in a first center position, which first center position is basically in the middle position between the first engagement position and the second engagement position and is basically in a first plane containing the first engagement position, the second engagement position and the first center position of the orbital axis of the movable scroll member or the longitudinal axis of the fixed scroll member that has moved.

[0018] The method may also include a subsequent step of rotating the eccentric member about the rotation axis of the drive shaft to impart an orbiting motion to the movable scroll. Then, while the movable scroll is orbiting, the orbiting axis of the movable scroll or the longitudinal axis of the fixed scroll is moved relative to the other in a third direction until the movable scroll engages the fixed scroll, the third direction being substantially perpendicular to the rotation axis of the crank and being different from, preferably substantially perpendicular to, the first direction and the second direction. At the time of the engagement, the one of the orbiting axis of the movable scroll or the longitudinal axis of the fixed scroll that has moved may be considered to be in a third engagement position.

[0019] The method may further include the step of causing the orbital axis of the orbiting scroll and the longitudinal axis of the fixed scroll to move relative to the other in a fourth direction substantially opposite to the third direction until the orbiting scroll engages the fixed scroll. At the time of the engagement, the orbital axis of the orbiting scroll or the longitudinal axis of the fixed scroll that has moved may be considered to be in a fourth engagement position.

[0020] The method may then include the step of positioning the orbital axis of the movable scroll member or the longitudinal axis of the fixed scroll member that has moved in a second center position, the second center position being substantially midway between the third engagement position and the fourth engagement position, and substantially in a second plane containing the third engagement position, the fourth engagement position and the second center position of the orbital axis of the movable scroll member or the longitudinal axis of the fixed scroll member that has moved.

[0021] Preferably, the second center position is also substantially midway between the first engagement position and the second engagement position, substantially in a third plane containing the first engagement position, the second engagement position and the second center position of the orbital axis of the movable scroll member or the longitudinal axis of the fixed scroll member that has moved.

[0022] In the case where the longitudinal axis of the fixed scroll moves relative to the orbital axis of the movable scroll, the engagement position and the center position can be determined using a fixed point on the fixed scroll. However, in the case where the orbital axis of the movable scroll moves relative to the longitudinal axis of the fixed scroll, the engagement position and the center position can be measured using a fixed point on the drive shaft. The planes (first, second and third) can be transverse to the axis of rotation of the drive shaft.

[0023] Preferably, the orbiting scroll moves relative to the fixed scroll. Preferably, the orbiting scroll moves relative to the fixed scroll by pivoting or translating the drive shaft.

[0024] Additionally, or alternatively, engagement between the fixed and orbiting scrolls may be detected by monitoring cessation of rotation of the drive shaft.

[0025] Preferably, the drive shaft rotates at a low speed, preferably less than about 5 Hz.Preferably, the drive shaft rotates in a direction opposite to its pumping direction.

[0026] Typically, the drive shaft is rotated by directing a gas flow through the scroll pump, preferably wherein the gas flow is introduced via an exhaust conduit of the scroll pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In the following disclosure, which is given by way of example only, reference will be made to the accompanying drawings, in which:

[0028] Figure 1 is a schematic illustration of a prior art vortex pump; and

[0029] Figure 2 is a schematic illustration of a scroll pump according to the present invention. DETAILED DESCRIPTION

[0030] The present invention provides a scroll pump, preferably a vacuum scroll pump, and a method for centering a movable scroll and a fixed scroll of a scroll pump.

[0031] Figure 1 A typical small capacity scroll pump (1) is shown. The movable scroll (2) is mounted on a rotating crank or drive shaft (3). Crank offset is provided by a sleeve (4). The center and rear crank bearings (5, 6) are held in a fixed position. In the example shown, the rear bearing (6) is held by a fixed bearing housing (15) formed integrally with the scroll pump housing (16). In the example shown, the radial clearance between the two scroll members (2, 17) is determined by nine components. The inventors have found that the combination of manufacturing tolerances on these components can produce a total deviation of approximately + / - 0.2 mm.

[0032] As the capacity of vacuum pumps decreases, internal leakage becomes an increasing problem for pump performance. Such leakage has a negative impact on ultimate pressure. In the configuration shown, it may not be possible to have a minimum clearance that will not get stuck, and also not be possible to have an average or maximum radial clearance that provides acceptable performance in a small capacity pump. For example, capacities below 5m 3 / h pump.

[0033] Figure 2 A vortex pump (7) according to the present invention is shown. The vortex pump (7) shown has a rear shaft bearing (8) which is movable so that the radial position of the movable scroll (9) can be changed. This adjustment enables the movable scroll (9) to be placed in a substantially optimal radial position so as to provide a radial clearance between the scrolls (9, 10) which is nearly constant in all crank (11) orientations. The optimal positioning of the movable scroll (9) allows a smaller radial clearance to be achieved than would otherwise be achievable, which in turn leads to improved performance, including lower ultimate pressure and power. The present invention therefore facilitates the provision of a smaller capacity vortex pump. However, those skilled in the art will appreciate that the method and pump construction can be successfully used in pumps of all sizes.

[0034] In the scroll pump (7) shown, the rear bearing (8) is mounted in a slidable bracket (12) forming part of the housing (18) of the scroll pump (7). The bracket (12) is mounted on the motor body (18) and has drive screws (not shown) for moving the bearing housing (8) in the 'X' and 'Y' directions. The pump (7) is reversed at low speed by applying 350 mbar of air to the exhaust of the pump (not shown). When the scroll members (9, 10) are pushed to the contact point, the rotation of the pump stops. In this way, the extreme position at which the pump (7) will operate can be found, and the rear bearing (8) can then be set to a substantially central position. This can be done in both the 'X' and 'Y' directions. The position of the rear bearing is then locked, for example by tightening the screws (13, 14) on the bearing bracket (12). The relatively low air pressure applied to the exhaust ensures that only a slight contact is required to stop the rotation, thereby avoiding damage to the scroll members (9, 10). The bearings (8, 20) shown are ball bearings.

[0035] In an alternative arrangement, the pump motor may be run in the forward or reverse direction at a low speed (eg, less than about 5 Hz) and a torque meter may be used to determine contact; when the torque meter determines an increase in torque attributable to scroll contact, the pump motor is shut off.

[0036] exist Figure 2 In the embodiment shown in , the center bearing (20) is held in a flexible bearing bracket (19). The flexible bearing bracket (19) can bend in the axial direction, but the radial movement of the drive shaft (11) is substantially eliminated during use. The flexible bearing bracket (19) combined with the adjustable rear bearing (8) can provide a high degree of control over the position of the movable scroll (9) relative to the fixed scroll (10). Typically, the flexible bearing bracket is metal, typically, the flexible bearing bracket is made of aluminum alloy or steel. Typically, during use, the flexible bearing bracket enables the bearing to move from about -0.5 mm to about +0.5 mm in the axial direction.

[0037] Unless otherwise stated, for the purposes of the present invention, axial and longitudinal directions refer to directions substantially parallel to the rotation axis (A) of the drive shaft (11) of the pump. Radial refers to directions extending from the rotation axis (A) of the drive shaft (11) transversely to the longitudinal direction.

[0038] In an alternative arrangement, the position of the rear bearing may be fixed, while the intermediate (or center) bearing may be movable. Both arrangements enable the orbital axis of the movable scroll to move relative to the fixed scroll. In yet another alternative arrangement, the fixed scroll may be movable relative to the orbital axis of the movable scroll. The movable scroll is a term of art and refers to the scroll that orbits during use of the scroll. It will be appreciated that the movable scroll itself may be fixed when the pump is not in use.

[0039] However, it should be understood that various modifications to the illustrative embodiments may be made without departing from the spirit and scope of the invention as defined by the appended claims as interpreted by the patent statutes.

[0040] Reference numerals

[0041] 1. Vortex pump (existing technology)

[0042] 2. Moving scroll (existing technology)

[0043] 3. Rotating crank or drive shaft (prior art)

[0044] 4. Sleeve (Prior Art)

[0045] 5. Rear crank bearing (existing technology)

[0046] 6. Center crank bearing (prior art)

[0047] 7. Vortex pump

[0048] 8. Rear bearing

[0049] 9. Moving scroll

[0050] 10. Fixed scroll

[0051] 11. Crank / Drive Shaft

[0052] 12. Sliding bracket

[0053] 13. Screws

[0054] 14. Screws

[0055] 15. Fixed bearing housing (prior art)

[0056] 16. Vortex pump housing (prior art)

[0057] 17. Fixed scroll (prior art)

[0058] 18. Housing

[0059] 19. Flexible bearing bracket

[0060] 20. Center bearing

[0061] 21. Sleeve.

Claims

1. A scroll pump comprising a movable scroll and a fixed scroll, a drive shaft for driving the movable scroll, a first bearing coupled to the drive shaft, and a housing element, wherein the housing element is movable relative to the fixed scroll when the drive shaft rotates to move the drive shaft in a direction substantially perpendicular to the rotation axis of the drive shaft to position the orbital axis of the movable scroll in a radial direction relative to the fixed scroll, and wherein, The first bearing is coupled to the drive shaft such that the fixed scroll is positioned between the first bearing and the orbiting scroll.

2. The vortex pump according to claim 1, wherein: A movable housing element enables its position relative to the fixed scroll to be selectively fixed. 3 . The scroll pump of claim 1 , further comprising a second bearing coupled to the drive shaft and to a bearing bracket that is flexible in an axial direction.

4. The vortex pump according to any one of claims 1 to 3, wherein: The first bearing is located substantially at a distal end of the drive shaft.

5. A vortex chamber for a vortex pump according to any one of claims 1 to 3, the vortex chamber accommodating the movable scroll member and the fixed scroll member, the movable scroll member and the fixed scroll member each comprising an axially extending vortex wall, wherein: The vortex chamber has a diameter of less than 5m 3 / h capacity, and wherein, when the movable scroll member revolves, the minimum radial gap between the axially extending vortex wall of the movable scroll member and the axially extending vortex wall of the fixed scroll member is less than 0.06mm.

6. The vortex chamber according to claim 5, wherein: When the movable scroll member orbits, a minimum radial gap between the axially extending vortex wall of the movable scroll member and the axially extending vortex wall of the fixed scroll member is from 0.01 mm to 0.05 mm.

7. A movable scroll and a fixed scroll of a vortex pump according to any one of claims 1 to 3, the movable scroll having an orbital axis and the fixed scroll having a longitudinal axis, wherein the orbital axis and the longitudinal axis are coaxially aligned with a deviation of less than ±0.03 mm.

8. The orbiting scroll and the fixed scroll according to claim 7, wherein the orbiting axis and the longitudinal axis are coaxially aligned with a deviation of less than ±0.01 mm.

9. A method for centering an orbiting scroll and a non-orbiting scroll of a scroll pump, the scroll pump comprising an orbiting scroll and a non-orbiting scroll that are maintained radially separated during pumping, the orbiting scroll being coupled to a drive shaft via an eccentric member, the drive shaft having an axis of rotation, the method comprising the steps of: a. rotating the eccentric member about the rotation axis of the drive shaft to apply an orbital motion to the movable scroll member; b. when the movable scroll member orbits, the orbital axis of the movable scroll member is moved relative to the longitudinal axis of the fixed scroll member in a first direction substantially perpendicular to the rotation axis of the drive shaft until the movable scroll member engages with the fixed scroll member, and when the movable scroll member engages, the orbital axis of the movable scroll member is in a first engagement position, c. moving the orbital axis of the movable scroll relative to the longitudinal axis of the fixed scroll in a second direction opposite to the first direction until the movable scroll reengages the fixed scroll, wherein the orbital axis of the movable scroll is in a second engaged position, and d. Positioning the orbital axis of the movable scroll member in a first center position, which is substantially in the middle between the first engagement position and the second engagement position and substantially in a first plane containing the first engagement position, the second engagement position and the first center position of the orbital axis of the movable scroll member.

10. The method according to claim 9, further comprising the following subsequent steps: e. rotating the eccentric member about the rotation axis of the drive shaft to apply an orbital motion to the movable scroll member; f. when the movable scroll member orbits, causing the orbital axis of the movable scroll member or the longitudinal axis of the fixed scroll member to move relative to the other in a third direction substantially perpendicular to the rotational axis of the drive shaft and substantially perpendicular to the first direction until the movable scroll member engages with the fixed scroll member, and at the time of the engagement, the one of the orbital axis of the movable scroll member or the longitudinal axis of the fixed scroll member that has moved is in a third engagement position, g. moving the orbital axis of the movable scroll or the longitudinal axis of the fixed scroll that has moved relative to the other in a fourth direction substantially opposite to the third direction until the movable scroll engages the fixed scroll, wherein the orbital axis of the movable scroll or the longitudinal axis of the fixed scroll that has moved is in a fourth engaged position, and h. Position the orbital axis of the movable scroll member or the longitudinal axis of the fixed scroll member that has moved in a second center position, the second center position being substantially at an intermediate position between the third engagement position and the fourth engagement position, and substantially in a second plane containing the third engagement position, the fourth engagement position and the second center position of the orbital axis of the movable scroll member or the longitudinal axis of the fixed scroll member that has moved.

11. The method according to claim 10, wherein: The second center position is also substantially in the middle between the first engagement position and the second engagement position, substantially in a third plane containing the first engagement position, the second engagement position and the second center position of the orbital axis of the movable scroll member or the longitudinal axis of the fixed scroll member that has moved.

12. The method according to any one of claims 9 to 11, wherein: Engagement between the fixed scroll and the movable scroll is detected by monitoring the drive shaft for stopping rotation.

13. The method according to any one of claims 9 to 11, wherein: The drive shaft rotates at a low speed.

14. The method according to any one of claims 9 to 11, wherein: The drive shaft is rotated by directing air flow through the scroll pump.

15. A method according to any one of claims 9 to 11, wherein the drive shaft rotates in a direction opposite to its pumping direction.

16. The method according to any one of claims 9 to 11, wherein: The orbiting scroll is moved relative to the fixed scroll by pivoting or translating the drive shaft.

17. The method according to any one of claims 9 to 11, wherein: The drive shaft rotates at less than 5 Hz.

18. The method according to any one of claims 9 to 11, wherein: The drive shaft rotates at 0.01 Hz to 4 Hz.

19. The method according to claim 14, wherein: The air flow is introduced through the exhaust pipe of the scroll pump.

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